1) Get the pet’s photograph and details onto this site urgently.
2) If it is a stray dog notify your local Council. (Not the PSNI!) and the Council will come and collect it. The vast majority of NI Councils are able to return the stray dog in a matter of hours. You can ask the dog warden to keep you informed about the dog.
3) Ring around the local vets, local Council and USPCA and ask if the pet has been reported as missing.
Remember if you do nothing then the animal may suffer. So when in doubt do something.