Rampart Raptor Despawned While Playing

Reference #3,079,385,374

While playing coop, my friend was using a mercenary with the unique Rampart Raptor crossbow. After outfitting the High Velocity Rounds ammo, he outfitted it with the Martial Tempo support gem. After doing so, I watched as his character's animations appeared to glitch out. Then, we entered the boss arena of Ervig the Druid in Act I, and he lost control of his character. The bow was dropped on the ground, and then it immediately despawned. It could not be found be either me or him anywhere.

Its a strange bug, but now we are left with no unique crossbow....