While I was trying to survive in the nether I wandered across a Bastion and I went to barter with the piglins and so I gave a gold ingot to a piglin and it did not appear in its hand but the bartering still works correctly.

Repro steps from comments below:

1. Put one gold ingot in your hand (more than one will not work)
2. Switch to survival mode with at least one piece of gold armor.
3. Right click on the Piglin with your one gold ingot. 
4. The piglin begins inspecting the ingot but it doesn’t appear on its hand.

Reported on Windows 10, Xbox One and Android