While I see your point and truth is we'll just never know, I am afraid you might be a bit naive.

I just don't see the circumstances for a random burglar to be snooping through folders close enough to find the presumably relatively hidden items they'd need to find, let alone that happening alongside the low odds an actual burglar would risk their own security to do the right thing.

This is exactly what burgling is. Having been the unfortunate victim once not even the spines of my books were safe. Burglars watch the same movies, so they will cut into your cushions, paintings, go through folders, behind outlets.

Then I got way too into a show about two ex burglars who would look for volunteer houses to break into, and yeah. No stone is left unturned and with far more diligence they would ever put in a real job.