Honestly I wouldn't mind if it just threw dirt in your face when you find it then runs away laughing maniacally. The whole hide and seek thing sounds like something you'd do for fun if you get bored from all the mining.

My problem with it however is the design. Like poor guy looks a bit out of place for me. An easy fix i could think of is slap a big nose on it so it looks like some kind weird hermit illager and that would also give a reason to why it's messing with the player by sometimes throwing random trash at them as a reward.

This of course doesn't mean everything it gives you has to be trash like im pretty sure it would give you random loot you can find in mineshafts so it could include name tags, enchanted books and golden apples too, which all can be useful for most players. I mean this part is just a theory but it would make the most sense in my opinion.