We understand that not all players would like to participate in the Crates and Keys system and prefer to get items through other means, such as game drops or Player-to-Player Trades. In-game, there is an option that allows you to hide your Crates and Keys from the inventory and any Crate Drop notification after a match.
This "Hide Crates" option may be found under the Options > Gameplay sub-menu.
If by any chance you do not see the Crates and Keys that you have or do not see any under your inventory after receiving them from a Player-to-Player Trade, make sure that you don't have the "Hide Crates" option enabled. As soon as you disable this option, you will see all the Crates and Keys that you have in your inventory as well as the Crate Drop notification at the end of a match.