I am guessing you're a woman?
He may or may not be intentionally trying to piss you off. It sounds like you like him. I am a man, on the other side of this same situation, where- I want to be friendly with my female coworkers, but then they start to really care about little things I say, and it just becomes a hassle. These experiences have led me to adopt an attitude that the workplace is not for friendship and normal human emotion, it's for work.
Regarding this one incident, you are overreacting, but that's okay and super normal. Just visualize the following: you zoom out from your body, and you are floating in the air, viewing your workplace from above. Next, zoom out and look at your city or town, then your state, notice how small you and your workplace are at this point. Zoom all the way out to the earth. Zoom out to the edge our solar system, and this entire earth, containing you, this annoying memory, your workplace, is smaller than a marble.
How big does this little event, these temporary feelings, the random info this guy chose to withhold look, from the perspective of infinity?
It will pass. Just let it flow past you. And finally, knowing how workplace "friendships" go, I've noticed that a lot of the time feelings develop. Consider this- we are animals. Consider the zoo- when they want two animals of the same species to mate, what do they do? They stick them in the same enclosure. It's normal to develop feelings for people you spend the majority of your waking hours sitting 6 feet away from while trying to focus on some tasks you'd rather not be doing. It's like an involuntary reaction of your body.
Consider this, he also has the same reaction to you. Maybe he's trying to piss you off, because he wants an emotional reaction out of you. Look at you, you're so affected and your mind is so on him, that you've gone and written this post. He's successfully gotten you to put all your focus on him, whether or not it was intentional. People do this all the time. People try to elicit strong emotions from each other, positive or negative, because it all counts as attention. But still, who knows how intentional it was.
All that stuff above is just food for thought. Here's what you really do: Try not to be too swayed by anything anybody says. In life, one of your goals should be to be stable regardless of whatever people might say. Aim for that goal. If you can't be happy and at peace independently of people's words, you'll sadly never find peace. I guarantee you, the thing this guy has said is nowhere near as big an event to him as it is to you. In that sense, this is really just your own battle. Your own reaction to sort of take a deep breath, and try and ride with gracefully.
In summary: It's not a big deal, and probably you're thinking about it more than anyone else. The event itself is inconsequential. You give people less power over you if you don't allow what they say or do affect you too much. And lastly, probably the reason you care so much is because you just like this guy on some level, and feel emotionally attached. Don't deny that either, just accept it, and think about what you would like to do next. Don't need to do anything rash like start aggressively ignoring him, because you probably don't really want that. It's usually not the best move to be reactionary. Better to just be cool, smile, breathe, look around, process things calmly. Good luck
