Pretty similar to the other stories about disappearing, but...
I used to live in this house that was built in the 1800's, and was converted into four apartments. At that time, only two other ones were occupied, one being the on call grounds keeper. He was an elderly man who would cut down a tree with no real reason, but he was still kind.
I started telling my friends about the house once the majority of the apartments were unoccupied, and eventually some of them moved in.
One day Lori, who had just started occupying the biggest apartment (upstairs and next door to the grounds keep's apt), came to my door and said it was absolutely BURNING HOT upstairs. I took her for an idiot and stated the obvious, heat rises, but she insisted I come upstairs.
As I was passing his door to get to hers, I noticed it WAS sweltering up there. I touched the door knob, safe, but when holding my hand at the base of the door, I could feel the heat just pouring out. After knocking several times, we began searching for a key to his apartment under the carpet on the stairs. We had come across so many keys, to our own apartments, we figured we'd find at least one. We were right.
We let ourselves in, and immediately found the source of the heat. The apartment was a studio, just one room and a kitchen. Against the wall opposite the door, the heater attached to the wall was on high, the coils orange. It had been on so long it had warped and blackened the mirror above it. (At this point we were well into summer)
The first thing I did was turn the heater off, then unplug it. Then I started looking around. Sitting by a chair was an almost full pack of cigarettes, a lighter, and an ashtray with a cigarette partially smoked in it.
I went into the kitchen and saw a bag of groceries sitting out on the table, all of it rotted and stinking. I managed to find a receipt in the mess, dated for December.
Basically everything in the apartment looked as if he was coming back shortly. When I called our landlady, she didn't seem to know much, either. Seemed genuinely surprised he wasn't there anymore, then promptly rented the apartment to my friend Stephen about a month later.