Just to confirm, are you talking about chests that aren’t owned by any player (like those inside NPC settlements and dungeons), or are you asking about chests that are owned by some other player that isn’t in your clan?
Because the latter should not be possible, but the former has always been possible, like @Kikigirl said. In fact, that’s how we used to work around an old bug back in the day, when chests would sometimes stop respawning their content until reboot (or until being destroyed).