Ring does not detect a thief

The ring câmara door bell did not detect someone who came and stole a package from my porch. It gave just a shot in one second, and two seconds later, it shows the package and person gone. However, it detected the post man putting the package on the rug, walking away, even when he was in my front door neighbor. But the thief, just one snap shot from when she was getting into the porch! So frustrating! Is there something I am missing on settings to get the important things, not all the cats from the neighborhood?