I used to squat in an unoccupied house that was for sale in Washington DC.
I knew the people who had recently moved out of there, and had a key to get in (The real estate agent put his own padlock on the front door, but didn't do anything for the back.) I only slept and showered there and used the electricity because it hadn't been turned off yet. Free living while saving my shitty working class wages wasn't so bad.
The house had a walk-in closet in the basement that I would sleep in with a sleeping bag (it was kind of uncomfortable setting up camp in a big empty room with hardwood floors, and the closet was carpeted & kind of womb-like.) I crashed there for four months without incident.
I knew the place back to front and had what I felt was a pretty foolproof routine. I wouldn't turn on any lights at night, I had a car that I parked down the street at the grocery store while I was in the house, I left no trace that I was staying there other than my rolled-up sleeping bag and Dopp Kit which I hid in the ceiling.
After a long evening at work, I got in at about 3am, and immediately went into the closet to get some sleep.
I don't know what time it was --it couldn't have been long after I dozed off-- but I was jolted awake by a ringing telephone. There were no phones in the house, I was absolutely certain.
At first it sounded like it was right next to me, but as I got up, it was actually kind of quiet...and it didn't stop. It just kept going. I went upstairs (with no lights on, mind you) into the master bedroom to try to figure out what the fuck was going on, and I saw a police patrol car pull up in front of the house. I started freaking out because the phone was STILL RINGING and there were now cops coming up who could very easily throw me in jail for vagrancy if they saw me.
They scanned the house with their flashlights, I assume to check the windows and doors for break-ins while I hid in the bathroom which had no windows. I always locked the back door so I wasn't in danger of them coming in. Sometime while they were doing this, the ringing finally stopped, but I never found out where it was coming from.
Scared as hell of the possibility of getting arrested, I waited until they left and packed up my shit and walked down the street to my car. By this time, it was early dawn and getting light out. I took a nap for a couple of hours, and drove by the house at around 8am to see a maintenance van in the driveway along with a person I assumed to be the real estate agent. I avoided the place for a week, couch surfing with friends, and when I came back, the real estate padlock on the front door was gone, and both the front and back door locks had been changed.