I don't agree with that statement. The reason most housewarming parties are thrown are for people to show off their new digs! Nobody registers for them so why would you think that they are for the owners to get gifts? You should take a gift, like a bottle of wine, home depot gift certificate or something like that, but housewarming parties are not done for the gifts. We waited till 10 months after we moved in to throw ours, I wanted our kitchen remodel to be done so we could show off dh's handiwork. We got an ugly vase, some ugly candle holders, a candle, a banana hammock, and I don't remember what else. I really could have done without those ugly gifts but it's the thought that counts!
To the op, I would get your coworker a gift. Nothing big, but a token gift would be nice.