My best guess is, someone had needed to move my coat and when they did, the pack of gum fell out, they saw it, and stuck it in a pocket so my stuff was still accounted for. Meaning someone was both a) paying attention and b) being conscientious with my stuff.
Quite a few of my previous jobs, I wouldn't have expected people to do that. Hell, one job I had for three years, a co-worker stole the coat I had at the time, and we never caught who did. (That was a bright yellow coat, too. Bright. Yellow.)
It's a small thing, but: thank you, whoever made sure I still had my gum.