Try to simply log-in to your old profile. You may have download/reinstall the old game. If this does not work contact the Steam staff (they are useless, but its still protocol). They will tell you to send a copy of your receipt, box, and code (unless they updated procedure) to them. You will have to pay shipping and a small "fee" for them to simply look at it.
Steam is the reason I became a pirate, they screwed me out a few games. I was not willing to pay 2x for them or their silly fees. I simply pirated the newer and better games as compensation for my frustrations. If you are not wanting to risk getting in trouble with your ISP, download the game you have the rights to. If they catch you (which is hardly ever) you can then prove to your ISP you bought the game way before downloading so you have the rights to owning it. They will pursue you any further because lawsuits are costly and your one of the "good" ones. I did this with Total War Medieval which I did in fact buy.