Part time job in Stirling - Customer?

Hello making this post anonymous as I dont want to expose where i work.

I decided to get a part time job in stirling over the christmas period. I have been working here for a week, and some random guy comes up to me asks "Cats or dogs" I say "Cats" and then he hands me an envelope covered in stickers, says "Merry Christmas" and immediately leaves, I open up the envelope and there is £50 cash inside, just money, no note, or anything. I'm grateful for the surprise, but very confused. I'm not from this country, is this normal? Has anyone else had this experience?

I saw him again a few days later handing an envelope to another employee in a shop across from where i work, but before I could get a chance to approach him he was gone. I just wanted to say thank you to this stranger, I don't know if he will see this, but it really helps with my bills this month, and is the nicest thing someone has ever done for me if anyone knows this man please thank him for me!