Did the guy get his cat back? That would be my first question. Cats are free spirits, they aren't required to be on leashes, so the guy shouldn't have told you his cats didn't come to your yard. They can.
Just remember it's not the cat's fault. I think I'd be ticked off too that you didn't at least check to see if the cat was his before bringing it to the police. Then you would have proven that the cats come into your yard because you trapped one and I would have then let it go into the care of it's owner.
When I was a kid, my cat used to frequent my neighbor's sandbox for their kid (who was my best friend). We share our surroundings with all the critters. Deal with it.