Unique items from villagers and sometimes levels are simply normal items with the unique tag and the orange tint around the item. It is most likely luck of the sea having an issue as uniques never appear in the village merchant trade window. The item sells for the typical unique item sell price for its power level. Since the white screen bug is currently affecting my game, the only way I can play is by going to the file location and opening it from there.

I've seen the reports of this happening with ancient hunts and items not being gilded, but I haven't seen any on normal levels and villagers.

Hopefully this helps.