Well, I sort of predicted it, but it actually turned out for the better. I was contacted by the company who has Leo's microchip registered and was informed that another owner would like to transfer the registration. This is good news!
That means that whoever adopted him is being responsible and cared enough to ensure that if Leo is lost, he will come back to them. From what my vet told me, very few new owners of previously owned animals actually do this, although I don't know why.
I asked the microchip company to forward my contact information to the new owners in case they would like to know a little about his past, but I haven't heard anything. I would love to have the chance to learn about his new life, but for now, I am happy to hear that his new mommy or daddy are caring for him and are thinking about his well-being.