Maybe he was just eavesdropping and found the conversation interesting.
Maybe he's just flattered because you are think he's cute.
Maybe friends in the office are not being 100% truthful because they enjoy teasing you about this.
Maybe you can find each other attractive but not follow it up because both of you are with someone.
Certainly you shouldn't be chasing one chap, while you are the girlfriend of another ~ that doesn't sound right.
It might be normal to find other men attractive whilst you have a boyfriend, but not to act upon that feeling.
