I have the addon set to automatically equip the Carrot on a Stick trinket when I mount. If I press mount again to dismount, loot an item, or a few other actions, the Carrot on a Stick gets removed and my normal trinket gets re-equipped.

However, if I press a combat ability (WITHOUT entering combat) the trinket does not swap back. For example, if I target an enemy and press a spell with a 3s cast time, but then cancel the spell, the trinket still never swaps. I would think it is supposed to work because my character is never actually entering combat.