If you think that this could only be a non-steam server that makes this happen I can prove to you that this is not the case. I run a HLDS server with all the legit setup for steam only players and if you connect to it it will say that your steam_id_pending. Now you know if you have steam so go ahead and connect and check status and you will see that I and others have this legitamate problem. Here is the IP address:
67.163.79.237:27016
Try it then come back with an open mind and see if you can help fix this instead of discounting it as an illegal copy of the game being played.