Why does he avoid talking to me after I said no to a date?

To make a long story short, I don’t really think guys read these blogs so I will provide plenty of details. All of a sudden this guy about 8 cubicles from me that I had only known as just one of the guys on the floor all of a sudden started buying me “payday chocolate bars” just about every other payday for about 6 months. He would not say much though, he was just like, “I went out for lunch and I thought I would get you one also, then he would just walk away. Finally, in early August, he waited for me to finish the day. He said, Any plans for this weekened, I was like I have to go, I just want to relax. He said “this has been a long summer, maybe we can get a bite to eat after work if you are free, my treat?” He is a nice guy, I just don’t seem him that way, at least for now-or maybe never. He really caught me off guard, I had an idea he liked me, but I did not think he would ask me out. I told him it was not a good idea since we are coworkers. He said, he was okay with my decision and even thanked me for allowing him to hear him. He really has to stop and talk to the accounts receiveable clerk two cubicles away from me everyday. In the past he would say “hello” now, it is the “hi” or just the forced polite smile with the pursed lips when has no choice but to confront me(we are part of the same organization). He now trys to stop by the accounts clerk when I am not around or when I am the busiest. Three consecutive paydays and no “payday chocolate bar.”
One day he did not even give me the nod or forced smile. He looked at his phone instead. As soon as he left my area he put his phone down. Just this past week, he attempted to act normal like all is well and even made small talk. Does this mean, he will try to come at me again? Does it mean, he is now over it? Also, no one has ever bought me anything prior to asking me out. Does it mean he really LIKED ME for more than just a fling or casual romance? Was he really HURT? If he is hurting, how long will it be before he is just normal again?