The shelter investigates cases of potential animal mistreatment but in this case the evidence was lacking for such charges.
"All evidence points to Zipper being left in the vehicle for a few hours during the evening he was taken in by police," a statement from the shelter said.
"While not ideal, and an absolute no-no in warmer months, leaving an animal in a vehicle for a short time is not illegal unless other circumstances pose a threat to the animal's welfare," such as extreme cold weather, the presence of dangerous items that can cause harm or leaving the vehicle unlocked, the statement said.
The shelter received numerous calls from people as far away as Florida and New York who were concerned about Zipper.
"We also want to recognize the patience and understanding of Zipper's owners, who have been distraught over the allegations of abuse made in online forums, as well as the separation from Zipper," the statement said. "They have been fully cooperative during our investigation and have complied with all requests made of them."
The pug-beagle mix was found in a vehicle about 1 a.m. April 21 in a West Seattle parking lot without food or water, according to the Seattle Police Department.
A security guard told police he believed the car had been parked in the same spot for at least six days and wasn't sure how long the dog had been alone in the car.
Police said they were unable to find the car's owner because it had been recently sold, so they removed Zipper and handed him over to the Seattle Animal Shelter after the security guards at the QFC at Westwood Village gave him food and water.
One guard told police he believed the car had been parked in the same spot for at least six days and wasn't sure how long the dog had been alone in the car.
The shelter investigated to find how long the dog had been left alone without something to eat or drink.
Evidence and numerous witness statements and a search of the vehicle, did not support the widespread speculation that Zipper had been left in the vehicle for up to six days.
Although the initial poilce report said he appeared to be emaciated, but the shelter said while he "could stand to gain a few pounds," it called him "extremely fit" after observing his eating habits and taking him to the vet.
So owners can be found if a pet gets loose or a situation occurs like what happened to Zipper, the shelter recommends that owners get their pets licensed and microchipped, and have a personalized tag with their contact information alongside the license on the pet's collar.