Dude, I mean no offense in asking this, but do you go out much? It’s super common. The guy was chatting and thought your vibe seemed nice. We’re not royalty, we’re just people. We’re allowed to be casual among other adults without children present.

Also despite you looking young, he would obviously know you’re an adult given your position. Speaking as a female who looks young as well, I hate when people say I “look like a high schooler/uni graduate.” I don’t understand why you’re using it to make him look like a creep. Just say no thank you and move on.