How to get apache to look for files in different subfolders folders

I am definitely new to mod-rewrite stuff.

Note:- here the URL is common, and all the folders and subfolders on same host.

The url a user uses to access their page is http://myurl.com/1234/filename.jpg

Here the name of the subfolder is an integer is unique and generated dynamically by another application.

The subfolder stores images specific to an individual user.

So the folder structure is as follows

main1 = document root
main2 is another folder within main1 or document root.

/main1/1234/filename.jpg
/main1/5678/filename.jpg
/main1/2345/filename.jpg
/main1/1212/filename.jpg
/main1/main2/2367/filename.jpg
/main1/main2/8790/filename.jpg
/main1/main2/9966/filename.jpg

So, I want to write a rewrite a rule so that if a user tries to type in

http://myurl.com/1234/filename.jpg,

the rewrite rule will need to look where the file is and serve the request; so for request http:/myurl.com/1234/filename.jpg the actual page is located at /main1/1234/filename.jpg and then need to serve that page from that folder.

So, if another users makes a request as http://myurl.com/9966/filename.jpg, it should serve the page from the following destination /main1/main2/9966/filename.jpg

Please let me know if the question is still not clear.

This is what i have done so far and does not work at all.

RewriteCond         {DOCUMENT_ROOT}/%{REQUEST_FILENAME}  -f
RewriteRule  ^(.*)$ {DOCUMENT_ROOT}/$1  [L]  
RewriteCond         {DOCUMENT_ROOT}/main2/%{REQUEST_FILENAME}  -f
RewriteRule  ^(.*)$ {DOCUMENT_ROOT}/main2/$1  [L]

any help is really grateful

EDIT
@ShaneMadden please find the details
The config is located in the .htaccess file; please find the .htaccess details

RewriteEngine on 
RewriteCond %{REQUEST_URI} ^/main1/\/. 
RewriteCond %{REQUEST_FILENAME} !-f 
RewriteRule ^(main1)(/\/.+)$ $1/main2/\$2

EDIT:

Olivier, thanks for helping me. please find the details as below..

httpd.conf

DocumentRoot  "/WebServer/Documents"

Directory Listing

ls -lRt /WebServer/Documents/

-rw-r--r--   index.html 
-rw-r--r--   .htaccess
drwxrwxrwx main1
drwxrwxrwx 456231 (Is a folder)


./WebServer/Documents/main1/:
drwxrwxrwx 566432

./WebServer/Documents/456231/:
-rwxrwxrwx  one.jpg

./WebServer/Documents/main1/566432:
-rwxrwxrwx one.jpg

.htaccess Files

RewriteEngine on

RewriteCond  %{DOCUMENT_ROOT}/%{REQUEST_FILENAME}  -f
RewriteRule  (.*) %{DOCUMENT_ROOT}/$1  [L]
RewriteCond  %{DOCUMENT_ROOT}/main1/%{REQUEST_FILENAME}  -f
RewriteRule  (.*) %{DOCUMENT_ROOT}/main1/$1  [L]

Access URL's –> http://localhost:80/

::1 - - [26/Nov/2011:10:52:54 +0000] [localhost/sid#10090f128][rid#1009918a8/initial] (3) [perdir /WebServer/Documents/] strip per-dir prefix: /WebServer/Documents/ -> 
::1 - - [26/Nov/2011:10:52:54 +0000] [localhost/sid#10090f128][rid#1009918a8/initial] (3) [perdir /WebServer/Documents/] applying pattern '(.*)' to uri ''
::1 - - [26/Nov/2011:10:52:54 +0000] [localhost/sid#10090f128][rid#1009918a8/initial] (4) [perdir /WebServer/Documents/] RewriteCond: input='/WebServer/Documents//WebServer/Documents/' pattern='-f' => not-matched
::1 - - [26/Nov/2011:10:52:54 +0000] [localhost/sid#10090f128][rid#1009918a8/initial] (3) [perdir /WebServer/Documents/] strip per-dir prefix: /WebServer/Documents/ -> 
::1 - - [26/Nov/2011:10:52:54 +0000] [localhost/sid#10090f128][rid#1009918a8/initial] (3) [perdir /WebServer/Documents/] applying pattern '(.*)' to uri ''
::1 - - [26/Nov/2011:10:52:54 +0000] [localhost/sid#10090f128][rid#1009918a8/initial] (4) [perdir /WebServer/Documents/] RewriteCond: input='/WebServer/Documents/main1//WebServer/Documents/' pattern='-f' => not-matched
::1 - - [26/Nov/2011:10:52:54 +0000] [localhost/sid#10090f128][rid#1009918a8/initial] (1) [perdir /WebServer/Documents/] pass through /WebServer/Documents/
::1 - - [26/Nov/2011:10:52:54 +0000] [localhost/sid#10090f128][rid#10099c8a8/subreq] (3) [perdir /WebServer/Documents/] strip per-dir prefix: /WebServer/Documents/index.html -> index.html
::1 - - [26/Nov/2011:10:52:54 +0000] [localhost/sid#10090f128][rid#10099c8a8/subreq] (3) [perdir /WebServer/Documents/] applying pattern '(.*)' to uri 'index.html'
::1 - - [26/Nov/2011:10:52:54 +0000] [localhost/sid#10090f128][rid#10099c8a8/subreq] (4) [perdir /WebServer/Documents/] RewriteCond: input='/WebServer/Documents//WebServer/Documents/index.html' pattern='-f' => not-matched
::1 - - [26/Nov/2011:10:52:54 +0000] [localhost/sid#10090f128][rid#10099c8a8/subreq] (3) [perdir /WebServer/Documents/] strip per-dir prefix: /WebServer/Documents/index.html -> index.html
::1 - - [26/Nov/2011:10:52:54 +0000] [localhost/sid#10090f128][rid#10099c8a8/subreq] (3) [perdir /WebServer/Documents/] applying pattern '(.*)' to uri 'index.html'
::1 - - [26/Nov/2011:10:52:54 +0000] [localhost/sid#10090f128][rid#10099c8a8/subreq] (4) [perdir /WebServer/Documents/] RewriteCond: input='/WebServer/Documents/main1//WebServer/Documents/index.html' pattern='-f' => not-matched
::1 - - [26/Nov/2011:10:52:54 +0000] [localhost/sid#10090f128][rid#10099c8a8/subreq] (1) [perdir /WebServer/Documents/] pass through /WebServer/Documents/index.html

2.) http://localhost:80/566432/one.jpg

::1 - - [26/Nov/2011:10:59:28 +0000] [localhost/sid#10090f128][rid#1009918a8/initial] (3) [perdir /WebServer/Documents/] add path info postfix: /WebServer/Documents/566432 -> /WebServer/Documents/566432/one.jpg
::1 - - [26/Nov/2011:10:59:28 +0000] [localhost/sid#10090f128][rid#1009918a8/initial] (3) [perdir /WebServer/Documents/] strip per-dir prefix: /WebServer/Documents/566432/one.jpg -> 566432/one.jpg
::1 - - [26/Nov/2011:10:59:28 +0000] [localhost/sid#10090f128][rid#1009918a8/initial] (3) [perdir /WebServer/Documents/] applying pattern '(.*)' to uri '566432/one.jpg'
::1 - - [26/Nov/2011:10:59:28 +0000] [localhost/sid#10090f128][rid#1009918a8/initial] (4) [perdir /WebServer/Documents/] RewriteCond: input='/WebServer/Documents//WebServer/Documents/566432' pattern='-f' => not-matched
::1 - - [26/Nov/2011:10:59:28 +0000] [localhost/sid#10090f128][rid#1009918a8/initial] (3) [perdir /WebServer/Documents/] add path info postfix: /WebServer/Documents/566432 -> /WebServer/Documents/566432/one.jpg
::1 - - [26/Nov/2011:10:59:28 +0000] [localhost/sid#10090f128][rid#1009918a8/initial] (3) [perdir /WebServer/Documents/] strip per-dir prefix: /WebServer/Documents/566432/one.jpg -> 566432/one.jpg
::1 - - [26/Nov/2011:10:59:28 +0000] [localhost/sid#10090f128][rid#1009918a8/initial] (3) [perdir /WebServer/Documents/] applying pattern '(.*)' to uri '566432/one.jpg'
::1 - - [26/Nov/2011:10:59:28 +0000] [localhost/sid#10090f128][rid#1009918a8/initial] (4) [perdir /WebServer/Documents/] RewriteCond: input='/WebServer/Documents/main1//WebServer/Documents/566432' pattern='-f' => not-matched
::1 - - [26/Nov/2011:10:59:28 +0000] [localhost/sid#10090f128][rid#1009918a8/initial] (1) [perdir /WebServer/Documents/] pass through /WebServer/Documents/566432