PSA
Please, please get your pets microchipped! If they become lost, they can be returned to you. Collars come off or get taken off. Microchips don't. In the article below, they talk about microchips "migrating". They can & I've personally had 2 friends whose dogs had their chip migrate but vets are pretty savvy on that issue these days & when they don't find a chip between the shoulder blades, they go ahead & scan the entire body.
What does it cost? It varies. It was $25 for my dog & that included the vet fee to insert it. Check for low cost microchipping in your area. Check your local animal rescue, places like Pet Smart & Petco & so forth & check with your vet. But I urge you not to wait. Just go do it now before you end up saying, "I should have done it a month ago & now it's too late because my pet is lost."