Got a number on a napkin… flattered, though not interested. Better to not text or to say thank you?

Well, I’m super flattered…I am working at a cafe and the man sitting next to me left me his name and number on a napkin, which said in writing that he thinks I am gorgeous and has an extra ticket to a comedy show tonight. He’s an attractive dude, seemed friendly, but I am happily in a relationship and not interested. When walking out he just slipped me the napkin on the table and said it’s for me, and to look at it later.

Is it better to send him a text politely declining, though thanking him for his courage and compliment, so he can move on and find someone else for tonight? Or should I not text, and avoid a situation of sending mixed signals/having a seemingly friendly dude actually become a creep because I gave him my number?

Advice appreciated!

UPDATE: thanks for the input everyone— seems like the risks outweigh the potential niceties so I’m not going to text him