When someone else holds the map ownership, they have ownership of not just the monsters they kill, but also the drops. Looting from someone's map, especially from a bigfoot, without permission of the map owner is bannable through the map looting rule. As such, you got a 3-day ban for your first offense. Please remember in the future to ask before looting from someone else's map. If you're unsure who owns the map, use the ~mapowner command.
Map ownership doesn't lock others out from looting items, that's determined by either whoever did the most damage to the mob/boss or if you're partied with those players. I'll check into this a bit more and will get back to you soon with a final decision.