I think you oversold it when you got to the part about all the kids coming out of the house and being so happy, and the dog being a memory of the father, and the mom wanting to give you money and inviting you out to dinner... it's just too much and it makes you seem like you're trying too hard. Cut it short; make the owner just a regular happy person, or a mom with a regular happy kid. Don't make it into a nicely wrapped up episode on TV.
Also you mentioned the dog had a collar. Most dog collars have an address or a phone number. Either that or dogs get a microchip in their shoulder for identification if they get lost. If the dog is as important to the family as you make it seem in the story it would have at least one of the two if not both. It doesn't make sense for you to hold onto the dog for three days if it has that information.
Finally all the work you did in caring for the dog for three day is a hidden DLV; what type of loser guy has the free time to make posters and put ads in the newspaper etc etc for a stray dog? Guys with a busy social calendar wouldn't have time for that. Again, why not cut it short: you park your car, see the dogs collar and walk the dog back to the house. If you want to make it longer, the family isn't there so you leave a note and go home and take care of the dog for a few hours. The family picks it up and then everyone is happy.
I love dogs and in my experience so do most girls so stories about animals and rescuing animals are DHV in my book. You just need to rework it.
~Antithesis