That is sooooo sad.

But I'm really sorry that they were gone before you were able to "help" direct them to the harnesses.
But you know the silver lining here? You work there and care about the animals. There are some people working at pet stores that don't care, let alone even know much.
So I know it's probably sometimes not fun for you to work there dealing with all kinds of people. But for every 5 that you can't help, there's going to be 1 that you can. Kudos to you!!