Piglins holding gold in the Overworld vanish when they turn into Zombified Piglins

I spawned a Piglin in the Overworld in a cage (as can be seen in the attached video). I continuously gave it gold. It returned items as expected. It also shaked. Then, the moment it turned into a Zombified Piglin, it vanished, leaving the gold behind. I am pretty sure this could be replicated.