Do you have a dog or cat? Does it have a RFID tag yet?
If not, go to your vet tomorrow and get one. Collars and tags can and do come off. The RFID chip is forever. It doesn't hurt the dog or cat, sitting just under the skin near the nape of the neck. Most shelters and rescues have the chip reader. Just do this. Your pet is worth it.
What brought this on? As part of a much longer story, we found a beautiful 18-month old female shepherd. She had no tags, no microchip, and had met the wrong end of a skunk. Without tags or a chip the chance of finding her original owners are slim.