When you right click while holding horse armor or wolf armor, you can prompt an equipping action like you can with regular armor; however, since it is not a player armor piece, it just vanishes into nothing.

Steps to Reproduce:

1. Obtain a horse armor (material doesn't matter) or wolf armor
2. Put it in a hotbar slot
3. Select it and right click
   • Observed: Item "equips" but vanishes
   • Expected: it does nothing