See all of the shared files in a Dropbox account

Not through the web interface or any other DropBox application.

However, I submitted a ticket to DropBox support and they were able to tell me the source of the event. Then the following exchange occurred.

Me: Is there any way I could have figured this out on my own or is this info available only from the back-end?

DB Support: It's only available to us here in tech support.

I had a similar issue, but in my case it was purely a misunderstaning of the Dropbox UI.

When you click the link in the email you get when someone shares a folder with you, there is a "Download" button up at the right on the website you come to (see this screenshot). I thought that button meant that I would download the files once to my local drive – while that is true, it turns out it was also the way to add the folder to your Dropbox.

In case you too missed the function of that button, just click it and select "Add to my Dropbox" (again, see the screenshot).