Ok so today when I went to switch users to my account, my installation of Win 7 Professional x64 screwed up a bit so I restarted to try and fix it. I was then greated by ticking from the HDD enclosure region with no boot up.
After unplugging all the HDD's and restarting it became apparant that none of the HDD's were faulty and it must have been my GTX 480.
I prodded the 480 and the fan realigned and now I'm sweet but when I came to start up Steam...

CRYSIS 2 WAS GONE!

Well it wasn't actually gone, all the folder trees were still in place and Steam recognized it however the Crysis 2 folder in C:Steam\Steamapps\Common\ is now only 544mb big.
Steam wants me to download all 9.5gb again.

Help me! What has happened here? It was working fine before!
Any assistence would be appreciated as I don't want to use half my data cap in the first day.

And people wonder why other people say STEAM svcks.

Next time do not buy your game through steam (unless that is your final option), that is all the advice i can give you. Just use STEAM for chatting, other than that dont get games through steam if possible.

Steam is a piece of crap when it comes to chatting, the only reason I have it is because of the deals available on occasion.
So it looks like I'm downloading it again then...

Why do you assume that Steam caused you to lose the files?

It's your own fault for not backing your steam games up on a HDD or partition.

IF you have set up some raid stuff and unplugged hdd-s one by one to troubleshoot problem then no wonder it got broken... especially if you are using somekind of cheap builtin raid stuff.

I really doupt that steam has any fault in this... honestly.

@Mad0ne: I am not using a RAID array and as I said above I'm fairly sure the problem was my Graphics card.
@Dexy_22: I really don't think that it should be necesary to make backups of all my Steam games considering it's not usual for large chunks of programs to disappear randomly.
I don't believe negligence has a part to play in this, all my other Steam game installations are perfectly present and correct, just Crysis 2 is causing the trouble.

At no point did I point my finger at Steam and yell "Culprit!". I honestly have no idea how this happened and I would appreciate some actual suggestions on what may have happened to create such a localized problem.