Component Identification – Identifying Broken Component in Amplifier Power Supply PCB

It's a GDT

What you're looking at is almost certainly a Gas Discharge Tube, or GDT for short. They are basically a spark gap inside a sealed chamber filled with a specific inert gas mixture -- this allows them to provide more precise protection than an air spark gap. They're used for the same things as spark gaps, though -- mostly, overvoltage protection as when they break over and start conducting, they will "crowbar" the overvoltage.

Fried bugs in an SOT23-5 package with carmelized epoxy toxic fumes

http://www.ti.com/lit/ds/symlink/tlv62565.pdf

p.s.

There is another SMPS , U20 which is likely for 3.3V USB and other logic chips.

Since this SMPS is located near the speaker port, I am having second thoughts about the function of this regulator. By tracing the output, you may find it is used as a boost regulator like +12V used for Speaker port amplifier (not visible) and the MOTOV1 port. Shorting either of those outputs may have contributed to the problem of fusing the regulator. Although they tend to have UVP, OVP, OTP features that only works if the sense input is not damaged. So handle with care and use a very low current limited lab supply in your experiments and gradually raise the current limit to 50mA with a preset voltage.