Hmm, in most cases there would be a protection stone in place, or some sort of project protection.
Hmm, based on the logic running through my head, I would say that in even the old guest world you would have a roughly 8% chance of digging up out of a mineshaft onto someone elses property. Of course this is considering the likely chance of digging up to any property, and the chance of that specific property being unprotected.
Then of course you must consider that if you were digging upwards, you most likely would have put the blocks you broke back so you could jump up higher until reaching the surface. Meaning most of the blocks would be placed back in relatively the same manner. Plus, certainly the top ground block would be the same as what was dug up. Considering this, you are only telling the truth if:
A) You placed random blocks on your way up, or didn't place the right block on the top so the owner of the build noticed.
B) You
were not trying to break in to that unprotected property
C) You
didn't break or place any blocks anywhere else
D) The person accusing you has an absolute hatred for you.
E) You stumbled upon a grief trap by mistake, and tried to break out. In this case you were still griefing, but this at least shows that you most likely have intent to play instead of grief. That is, assuming everything under this idea is true.
F) You had no clue about the /home and /warps stuff (Thanks DJ, saw your post before posting this reply)
My logic does not point me in the direction of you telling the absolute truth. Perhaps you stretched the truth a bit, but it's hard for me to come to the conclusion that you told the absolute truth.
It also appears you have the ban history of a griefer. Ban after ban after ban.
http://www.opticraft.net/index.php/page,BanLookup.html?username=ultraman11