How do you ask for address of pet owners you had stay with you?

All my boarding clients fill out a Dog Info Sheet. All important information must be provided and that includes their address, phone numbers, emergency contacts, vet, etc. No one has balked or refused to provide that information.

I would think you want the address of any pet who boards with you. Let's say there's a power outage, the owner's cell phone took a dive, there's (God forbid) a raging fire in your area, etc. you may end up having to bring the boarding dogs back to their owners for any of a number of reasons. "Emergency Contact Information" for pets who board with you would include their street address, an emergency contact (spouse, neighbor, sibling of the dog's human), vet, etc.

The gift is just a side bonus of having that information.

You can reach out directly to the sitter via text using the number assigned during the booking process. I'm pretty certain the sitter would love to hear from you and provide their home address.