A tone at 8k is very directional, very hearable, and won't penetrate most solid walls.
There may have been other elements to the sound, but if that 8k was there, all you had to do was locate the sound by ear and say wtf, maybe put in some foam earplugs, go to a different room or leave the building. I do that kind of thing all the time in response to noise.
I don't get it.
Could you sleep through some "sonic attack" that was damaging your hearing?
It seems too weird to be true, but maybe.