Why a tattoo? There is no way for a shelter to ID him and contact you with a tattoo.
Tattoo's are typically used by breeders to ID their litters. The USCA uses them when a dog is trialing to ensure it's the right dog.
A microchip is really the way to go.
It's MICHELLE, scarfish! My name is MICHELLE! Jax is my DOG!
~The strength of one's opinion should not exceed their knowledge on the matter~