Agreed. I do know one of the two players though, he messaged me to let me know they meant no harm, though they were coming in a pair and wielding their weapons and all...I was having problems with my internet with lag and getting disconnected too, which made it all worse....I heard them breaking blocks and then I got disconnected! I don't really feel like they meant to do damage though, I think it was more curiosity...they heard cattle underground and me sorting through chests....just wish they'd closed up the hole behind them.
I've been checking the limits now with a bucket of water and then placing my walls inside of that....I'd forgotten when I moved the sponge over one block it would leave one wall underground vulnerable. There's not like a command that will actually show the border of protection is there?