When I search for things I do it in a few ways; Try Playstation 4 first Then Play Station 4, then ps4 Then just Playstation / Play Station
Because people list things all the time with errors or leaving information out or typos. I've done it quite a few times too and I never noticed until after the auction was over 8)
There may not be any ps4 games right now, but try searching once every 4-7 days and there is bound to be one!
I'm constantly surprised at the things given away on here, you just have to keep looking and be patient!