The neighbor's van

So, for the past year (or longer?), my neighbors behind me had parked their big Ford van alongside my backyard. Not a big deal, I don't use that space. But they never drove it, started it, moved it. In fact, it wasn't even pulled correctly up to the curb. Well, about a week ago, I came home and noticed that an orange sticker stuck to the windshield. I wonder if someone (not me) complained about it. (I just hope they don't think it was me.) Then I came home Tuesday and the van had been moved to their side of the block, next to their house. Sticker's still stuck to the window....