Good job. As everyone says, we all pay for someone else's five finger discounts.
Unfortunately, as far as chasing them down, it depends on what the store's policy is on theft. Some go after all and other's feel there is an acceptable amount of loss. I wonder if they had a security camera to track things like that. I know some stores do have the monitoring systems at the door, but they go off so often it seems like those are useless, because I have seen the employees just wave people through after they've gone off.