Easier way to get the GUID in Windows is to use the command OTOY recommended..

wmic PROCESS get Caption,CommandLine | FIND "GUID"

but write the results to a txt file on the desktop. So...

wmic PROCESS get Caption,CommandLine | FIND "GUID" > Desktop\t.txt

I don't know why OTOY would NOT have put that value in the instance metadata on startup???

You have two choices - supply your own GUID in the metadata, and this overrides the randomly assigned one, or look in RDP/ssh for it (which is more work than needed - highly recommended you add your own GUID, this way it doesn't need to be copied or grabbed from RDP/ssg)