Actually there are two ways one can lose the mining gloves.
1. You don't repair them, and eventially they hit 0 durability and break.
2. Verite & valorite elementals can break them. The item breakage code was supposed to have been removed from those elementals, but apparently still exists, at least for the mining gloves, and "reversed" armor items that are turned differently than the crafted version of the armor faces.
I've lost 3 pairs of mining gloves to sudden breakage (while at near maximum durability) in combat, over 5 years, with the high-end ore elementals that had armor breakage capability for all armor prior to AoS.