system
A chat on subreddit /r/NoStupidQuestions
human
I worked retail awhile back, had this exact scenario happen to me, as soon as I saw what was in the envelope, I dropped it back on the desk, showed my hands to the security camera and called a manager.  The manager did the **exact** same thing, then with both of us keeping both eyes on the envelope, we took it to our cash office, put it in a larger envelope and wrote the time, date and location in which it was found and put it in the store's safe.  Dude came back eventually.
gpt
&gt;I dropped it back on the desk, showed my hands to the security camera and called a manager.

Thing is though that if you found it and wanted to keep it you'd keep the lot. You'd hardly steal some and hand the rest in. How stupid would that be? 
That's why I never understand the idea when people get their purse back or whatever that they think somebody might have stolen money from it. If a dishonest person came across it they'd surely keep the whole thing.