I can assure you that if you take the dog to Doha Vets you will not be charged for having the dog checked for a chip. They will help you take care of it if necessary and most of their clients on the database also have a photo of each pet. You may be able to look through the system and see if it matches any pics.
Give them a call on 4367187 ask for Kim the manager, she will be able to help you, I promise