Thought I'd pass this from my original post in the steam forums, see if anyone here can help me with this.

"So yes, I had the "Clean up the killers mess" bug when I first got Hjerim and finished the quest, but thankfully a mod helped me take care of that. Unfortunately a new problem has come up.

I have a feeling this may have come from some advice when I had an additional problem when I got the place, when the house didn't clean itself up properly all over, aka the rotting chairs and furniture would still be there along with pieces of stray metal on the floor. I recall getting some advice to use the console to remove those manually, but I fear I may have removed a floor panel by accident, showing nothing but a blue space where the floor panel used to be! Reinstalling hasn't helped any, but if anyone has any advice on what I could do to get it back, such as the console command, I would be much obliged.

Oh, and just for those curious, if you walk on that missing tile, you fall through the ground and end up back just inside the door."

A user did try to help, but unfortunately to no avail. Would anyone here be able to help? Also I tried to post a link to a picture, but it wouldn't let me. >.<

Unistall the mod and start over again....

Did you use the disable command to remove it? If so, go into the CK to find its ID, then go back in-game and enable it. If you used markfordelete, I think you're screwed.