there should be repercussions
a good point !
the game already tracks ownership of inventory items. if the player picks up an item they don't own and are spotted, nearby friendlies will become hostile and attack. i'd have to double check the code, but that's the behavior as i recall. attacking NPCs has the same effect.
back when i was thinking about adding bands with goals, one part of it was nearby friendlies ganging up on the player's band for demanding tribute. i guess that would have to be added.
perhaps theft and tribute could be combined? if you tried theft on a band at their camp and suceeded, you'd get their trade items as well as what they had on them, instead of just what they had on them.
but if you succeed at a theft, the only repercussions would be negative relations with your victims. the next time you encountered them, the slightest provocation would make them hostile, but that would be it. other than that they would simply refuse to trade etc. it not like someone might come after you someday, unless i add that feature to the game.
if the player encounters a caveman who robbed them before, they are welcome to try to take revenge and attack them.