This happened on September 23, 2018, around 10 A.M. Or so.
It was a Sunday morning, and my roommate was at Service, so my cat and I were enjoying some uninterrupted TV time. I was enjoying a scary movie (my 'guilty' pleasure) with the drapes drawn and lights off for atmosphere. When out of nowhere, 3 loud bangs came from the wall behind me and to my right. Both the cat's and my heads whipped around to where the noise came from. Although, the room is dim, it is not dark at all, and there's nothing to be seen.
Perhaps the slight tingly feeling I'd had was not movie induced after all, I thought to myself and said, "Hello?" aloud. I knew I was the only one in the building at the moment. The downstairs neighbors had gone to the city taking their dog with. So, it wasn't something they were doing.
I went back to watching the movie, and again I hear "bam! Bam!" like someone hitting the wall flat handed. Again I stare at it. The other side of that wall is the bathroom, and it sounded like the sound originated from there.
Off I go to investigate.
The bathroom door opens inward, and I discovered what clearly appears to be a white handprint on the wall that's behind the door when opened. The same wall, I heard the banging on. It's in an illogical place; if you had your hand there, you wouldn't be able to open or close the door. It appears to be of the left hand, and is too large to be mine or the roommate's.
An interesting note, is you can tell that at some point there had been a door there. You can see a faint outline where they hadn't filled it in properly with joint compound. The handprint is almost in the center of the upper half - where one would hit if trying the handle at the same time.
I stared at what was undeniably a handprint for a long time. When you're on the toilet you face that wall, and I knew that it had not been there before. It was so white it stuck out like a sore thumb.
I went and got my cell to snap a picture, before doing a more physical examination of the print that might alter it, or for all I knew it might even just disappear. While snapping the pic, I talked to the air. No responses though.
Except for the coldness of the wall, there was no 'feel' to the print; slightly oily, or powder residue, etc. Didn't smear when I rubbed it either. Nor did I detect any emotion with it, at least none that might not be my own: a bit of nervousness, slight annoyance.
Later, I easily wiped the print off using just a cloth a water - no scrubbing at all. So far it hasn't returned either, but then again this apartment seems to experience a lot of one off things.