Some random stranger walks up to you, says "Thank you for last night", and then hands you 1000 bucks/quid/Euro. What do you do? [P.S. Do you know any slang terms for Euro?!]
"I think you have me confused with someone else." and maybe "I don't know you."
I'd hate to take their $1000 that's meant for someone else, unless they're rich af, but I wouldn't know that.