If you have acquired (purchased or been gifted) anything from Steam in the last week, I highly recommend that you make sure the games are still on your list.

Steam apparently had some kind of database error and they had to restore from a backup.
Games will ether not so up on your account, or will show as "Pre-load Complete", also Steam avatar pictures have been reverted to about 3 days ago.
I have lost about 8 games and my avatar has been reverted myself.

If you are missing a game I highly recommend that you submit a support ticket.
You will need to create a Steam Support account in order to submit a ticket if you do not already have an account.
You will want to use "Account Questions" > "Missing Games on Account" for your ticket.

[Steam Support: New Ticket]
[Steam Support: Create Account]