You either did one of three things:

(1) Accidentally click the "Put up for Adoption" which basically deletes the pet.
Solution: If its deleted, you will have to buy another one. Check each household to make sure.

or

(2) Relocate the dog to a different house than you intended to.
Solution: Again, check each household.

or

(3) Relocate the dog to a house, and the dog is just hiding somewhere. Especially, in the larger lots and in more complex houses, the dog is usually hidden from view.
Solution: Navigate the camera in the household. If you want an easy check, buy a dog bowl(Food at 10,000 Simoleans or Water at 8,000 Simoleans), have a sim fill it if not already filled, and do the action "Call Over". If the dog is there, he/she should come.