We were in Tunisia last month, staying in Sousse.
One evening we were walking in the city centre and were stopped by a polite young man claiming to be a waiter in our hotel. We didn't recognise him, of course, but in a large hotel with 100+ staff this is not surprising.

He invited us to a bar, which we declined, and then asked us for "help" - i.e. cash.

This is quite a clever approach - playing on your embarrasment for not recognising him - and might be quite successful. We didn't see him at the hotel, and I guess a way to call his bluff would have been to ask him to name the hotel (we thought of that afterwards!. Probably worth a couple of Dinars for cheek, anyway.