[PSA] Games disappearing from Steam

Within the last 4 hours, my bot had dozens of games disappear from its inventory. These games were not traded or stolen - they do not appear in the trade history or trade offer history. They simply disappeared.

The games include:

• 13 copies of Garry's Mod
• 4 copies of Castle Crashers
• 4 copies of Gone Home
• 6 copies of Counter-Strike: Global Offensive
• 2 copies of Binding of Isaac
• 9 copies of Space Farmers
• 4 copies of Mount Your Friends
• 2 copies of Bioshock Infinite

plus various other games.

If I view my trade-history and look for any of the above games, I can find the trade where I received one of the above games, but the trade is empty. Furthermore, previous copies of these games I traded away also show up as empty. For example, here is a trade I made earlier today, trading a copy of Garry's Mod for 2 keys:

http://screencast.com/t/ySER4odhFWiW

And here is (what I assume is) that copy of Garry's Mod in that user's profile:
http://screencast.com/t/j8RIyutS
http://steamcommunity.com/id/mrgiuli1t/inventory/#753

My trade-history is filled with similar empty trades.

Just a heads up to everyone else, if you have copies of any of these games you may want to check that they haven't disappeared...