I have the bug too.
For some reason my sims would not stop grilling stuff and then leaving the food out to rot without eating any, so I removed the grill. It had half-cooked asado on it. I took it out of my inventory to delete it and it became glued to the kitchen floor.
My sims show the same behavior of not being able to clean it up, I think because it's supposed to be attached to grill animations. They sure react to it when it starts to stink, though! Resetting it so it at least isn't rotten doesn't seem to work either. I tried putting the grill back and reuniting them, but that doesn't work either.
I've tried using testingcheats and the various object codes to try to remove it, but as the OP describes it's not a clickable object in build mode. The sledgehammer says it's not a deleteable object and deleting the floor under it does nothing. I even saved the lot and re-placed it, and tried moving the room to another part of the lot, but it's become this permanent disgusting design feature of my custom house!
The one thing I could do was create a little room around the food, and then move that room out to the yard. Now I have a little shrine to some stinky half-cooked asado in my yard, but at least no one's likely to be bothered by it out there...
I just had the same issue. Tried everything, then your idea of creating a little room for it. I moved it outside, the used a sledgehammer on it. The food reappeared in my household inventory - but now I know not to put it out anywhere!!!
