Games uninstalled?

maybe your pc had a problem and it reverted to a previously saved state, not sure though

As in steam not being able to tell that they are installed anymore? Try to re-download one of them. Steam should find the files (if the game is in your steam game folder).

Check your library folders settings.
Edit: This obviously applies only if you install games to more than one location

Do you mean that whatever\Steam\SteamApps\common\ is almost empty ?

that's quite strange :O

maybe you got gremlins. :P

maybe steam got something wrong or your library got messed up. try to redownload or check your settings.

*edit: wow, way too slow :S...

What if your operating system detected and destroyed all the pirated software!
Or it could be a virus, which was deleting every other soft but when you turned your PC off, he stopped at 38th game only!

accidentally activated "Steam in-Home Sharing"?

http://forums.steampowered.com/forums/showthread.php?t=2900691

Else maybe bad hdd?

Happened to me before. I simply prompted to "download" those games again and Steam actually just needed to verify the files again at the same disk drive. Not sure how this happens though.

Thanks for all the ideas guys! I got distracted by SG and went back to Steam and they're all there.....No idea what happened.

I'll just give you all a puppy photo and slink off to my games now.

View attached image.

If you have Win 10, there is an update that reorganizes your computer such as turning on privacy settings that were turned off by you and even uninstall certain programs.

I have the same problem with large games that I don't play a lot, CSGO disappeared mysteriously like that 3 times last year.
But smaller games that I don't play a lot don't seem to have that problem.

if you had a lot of racing games Formula 1 racing cracked down a lot on trademark and texture piracy which caused some games with pirated F1 content to be removed from steam