The first step is to register the missing pet LOST on a Petco Love Lost account. See instructions on How do I report my lost pet?
After marking your pet as lost, navigate back to the My Dashboard page. Find the picture of your pet under the My Pet heading. Under the picture of the pet you want to search for, click on the Options link. A small pop up will appear. Click on the Search for Pet link.
A quick search according to your listed zip code will display found pets in your general area. It is recommended to make your search as broad as possible. You may login and conduct new searches as often as needed.