The guy I like could be a thief?

We went for a walk and went to the library cause it was really hot. He was hungry so he asked if I had a dollar cause the library serves little snacks for a dollar. I said no, so he said okay. A few minutes later I was looking for a book and he had a muffin in his hand. I asked him if he found a dollar and said no. I gave him a look (because I HATE thieves. Because of my past with my mom being a theif etc. WHICH HE KNOWS ABOUT!) then he quickly said "It would feel to bad taking this" so he put it back. That was a few weeks ago. He's sweet, funny, caring, etc. My dad doesnt like him, but hes never really met him. My dad has called him "sneaky and a liar". That situation just kinda made me think. I really like this kid, but that day at the library, when ever I think of it...it makes me sick. :/ What should I do? Im almost 15.