Ah, that makes sense. I actually discussed the ban with a roommate, and we came to the same conclusion as to the cause.
As a side note, the reason I wrote "Help" on the wall was that there seemed to be no exit from the area. I built a nether portal in my home, used it, went back through the same portal in the nether, and was deposited in the underground room in question instead of back at my home. I'm not sure if this is a known issue or not, but I wasn't sure what to do.
In the future, I won't put extra blocks there haha
Thanks for the heads up!
Valoram