What is it?

I was going through some pictures that I shot last year and came upon this one. I remember it and have always wondered what it is.

It is on the roof of a building; I shot the photo from a much higher roof.

From the area of town, I suspect that it was tossed up by a thief. Maybe one being pursued. Or maybe it turned out to be of no value. If of no value, why toss it? Why not just drop it in the alley?

It was probably nothing.

But maybe I should climb that roof and have a look.