Armor disappears after death

When I die to a group of zombie pigmen, I lose my armor. After respawning, I go back to where I died and pick up all the items that I dropped upon death but find that my armor pieces are missing. This has happened to me at least five times now. Every time I lose either my helmet, my boots or both my helmet and my boots. But I never lose any other items. I am assuming that one of the zombie pigmen is equipping the helmet or boots and then despawning once I leave the chunk by dying, but I have no way of confirming this.