Not all cops in all places are all bad all the time. They’re always part of a deeply broken system and all the other parts of the usual rant about cops, but that doesn’t mean they never do a good thing.

Most cynically: it’s basically a free bump to their performance numbers.
Most leftishly: a business called, which is closer to who they work for.
Most probably: theif was still there and someone was close enough that they’d be doing more than taking a meaningless report to file.