actually, didnt work for me for mounts I learned that kept the same name as the mount item. Somehow my cache kept seeing the name as an item in my bag, despite it being in my spellbook now.

Deleting wdb helps for that.

You wont encounter this problem for most mounts. For example, Item "Horn of the Frostwolf Howler" became the cast "Frostwolf Howler" so wont become a cache problem.

Swift Zhevra -> Swift Zhevra however, you need to empty the cache for it or it will keep trying to locate the one in your bag.