This article explains how to view hidden games in your Steam library. Games that you have deleted will not appear with the following process, so be careful when deleting games from your Steam library.
How to View Hidden Games on Steam
Once you hide a game on Steam, it will no longer appear in your library and you will no longer be able to search for it in your library. It may seem like the game is gone, but it is certainly not, and it only takes a few clicks to find hidden games.
As long as you have Steam installed on your computer, you have everything you need to view all of your hidden games in your Steam library.
Open Steam. Make sure you are logged into your Steam account and of course connected to the internet.