I hope you aren't completely eliminating any other possibilities.
There are many, many other things that you could not be aware about that could play into this.
I'll explain my point. They were raiding a vault, which was underground. The vault was nearby me and jacks girth base. They Withered the base, got in, but cos of regen chests, got nothing. Only Jack being an idiot and giving them 3 blaze spawners lol. I honestly couldnt care, I killed Trump and got a rare voter set, savage axe, and rare voter sword and Bow. My point is that after, I randomly went to the underground vault, and saw them digging towards it. They were not "Checking under the base" Because it was unclaimed, and there were a million different places they could have looked, but they looked specifically in a place NEAR the base but not under it. It was 2 Chunks away from the base. So, it wasn't under, why look there? That Eliminated Squared's Theory. The /Near theory is bullshit, as they had been digging way before anyone had been to the vault in hours.