This is a bit of an edge case, as the average player would not have access to the command anyway. However I figure I should report it for completeness. If you use the /loot give @p loot minecraft:chests/shipwreck_map command, even near a buried treasure, you get a "Working..." map in your inventory which never updates to the actual buried treasure map. I assume this is because you designed the code to assume the map was within a chest instead of the player's inventory.

I confirmed that this occurs both on 1.20.1, and my 1.16 backport in ModernFix.

(I thought I'd replied to this before, but maybe it didn't go through or I imagined it)

Oh yes good catch, I hadn't considered that source of getting a map. I'll work on accounting for that, thanks!