The US Auto washroom key does not disappear from your inventory after unlocking the washroom to complete the Uncrate mission. I saw a few people on the Gamefaqs board still have the key in their inventory too, but did not see any mention of this bug here.
There are 5 other keys that still showing in inventory and 1 collectable set after completing the grand slam baseball set all ._._._....___. which makes there are 6 keys and 1 collectable