I never have, and it's obviously safe enough that thousands of people do it everyday, though not by choice.
If you don't see any signs of others staying there, don't assume it's safe, but you don't need to EXPECT someone to show up. Still prepare for it, of course. A pretty common method to alert is to set up a physical alert, or as my SO calls them, leprechaun traps.
Here is an example from my last trip:
1. Leprechaun Trap lol. Note 720170827_134345
by Rose ByAnotherName
, on Flickr
I was going to the roof, while they were further exploring the top floor.
So when someone opens the door, trap goes off, and alerts you. It's the only entry point, so that's that. They are easy to setup, and can really be done for anywhere.
I'd also have an escape plan set up. Most likely a window, where you could drop out, and the threat would not be able to reach you in time. A simple door would stop any wild animal, and an LT would alert you of attempted entry. One could also use something like a wedge or door bar to just hold a door shut.
One other thing to keep in mind, is what your value is to someone else. If your Lamborghini is parked out front, and you're Columbia Jacket is hanging up, with your expensive camping gear spread around, you could be a target to someone who stumbles on you. In a Goodwill jacket, with a rumpled sheet for a pillow, you'd be less of a target.
Finally, for however long you plan to stay, track what you do at home. So if you want to arrive at 1800, and leave at 0800, write down ALL that you do in the window, and plan that for the trip.
Play on phone.
Plug in phone.
Go to sleep.
Seems silly, right? But you'll need food. Just take what you need, maybe a bit more. It's not a week long exploration into a crypt. Poop. Got tp? A toilet seat, milk crate, and garbage bag? Play on phone. Are you bringing a book? What will you do between infiltration and sleep? Explore and shoot, sure, but the REST of the time? Do you have phone power to sustain? Pee. Got bottles? Brush teeth. Skipping, Listerine strips, full kit? Water to rinse? Spitting in pre bottle, or out a window? How will you charge your phone overnight? Sleeping arrangements?
So the silly little list sounds, well, silly, but if you will make shift live there for a day, be prepared! (Also, keep your stuff packed unless actively using it, in ONE bag, so it's easy to bail.)