I agree that you should check your admins. Was in the mining world and an admin asked me if I had created a town. I asked him why he was asking. Next thing I know he says something like "whoa nvm." A little while later I go back to my town and there's a hole dug through a space I was going to make a window in. I check my chest and the 5 diamonds I had mined the day before were gone.
As far as I know there was no command to lock chests, and many of the town commands don't seem available to non-members. I doubt I will be going back, but if you want my suggestion I would set the default town permissions to lock out outsiders. That wouldn't stop admins from abusing their power, but at least it would rule out anyone else greifing/stealing. If something happens, then you know it has to be an admin.
Could have sworn I set the permissions for guests to protect. Ill have to look into it. On the subject of the admins they have never done anything since the server opened. They are far more advanced to need to steal any supplies. They have tons of stuff that they don't know what to do with. I will look into all matters though