Ok... I ran across a situation today, and want some advice on what to do in the remote chance that it happens again in the future. Besides, it might help some other person out as well.

Trink and I were at the dog park for our normal Sunday morning playdate. Walked back to the car, put Trink in and got her settled, reached around to get the water jug and turn-out muzzle, put them in the front seat, and then felt a furry brush on my outside arm. I turned around trying to figure out how Trink had possibly gotten past me... and there was this little fuzzy white terrier, eagerly trying to get into the car!

There was no one around, no open garages or doors (I park on a residential side street, so my first thought was that the dog had slipped out from a near-by house). This little dog was plump and not matted or dirty, so obviously hadn't been running around too long. And it didn't want to leave my side. I tried calling the phone number on the tag, but my cell phone was dead. So then I went to nearest house and asked if they knew who had the dog. They didn't, and when they tried calling the number, the "customer was unavailable", with no voice-mail. And that family was getting ready to go out, and didn't want to be responsible for the dog.

So I was headed back out to my car trying to figure out what I should do. Putting a small, hyper, fluffy white dog into a car with an ex-racing greyhound wasn't seeming like a very smart idea to me. Leaving my dog in the car while I tried to find who owned the white dog wasn't going to happen, either... not with the temperature climbing. But just leaving the dog to wander around some more didn't seem like a good thing, either. Thankfully, as I got to the car I saw someone coming down the street, who turned out to be the dog's owner out looking for her. So it all ended happily in this case.

But what should I have done, if that hadn't happened? Tried taking the dog with, and hope that there wasn't bloodshed on the way? Or left the dog and tried contacting the owner when I got home to let them know where I saw the dog? Or some third option?

If it were me, and a dog came around that looked like it had a family that took care of it, loved it and would obviously miss it,
I wouldn't take it home with me unless I exhausted all other options.
Where there is a happy, healthy, clean, pup with a collar and tag, there is more than likely someone who is missing it or looking for it.

I'd practice being a good samaritan and of course make the calls to the numbers on the tags and walk door to door asking neighbors if they knew who the dog belonged to.
Usually at least one neighbor will know who the pet belongs too, if one house don't know, I'd try another.
I'd probably even ask on other roads close to the area as well.

As for your dog being in the car, I'd place the muzzle on him and secure him with the leash while you drive door to door. This way he is not being left in the hot car alone, but safe from getting into trouble with the other dog.

If after trying all that and nothing, I'd take the dog for safety reasons, but come back later to try the whole thing over again.
I'd post found signs on the roads, by the dog park and place a found ad in the paper.

If someone is looking for the pup, they will be sure to see the signs you posted in the area and may even check the lost and found section of the paper.

Also, most pups that stray away from home usually know how to get back.
If it's a quiet neighborhood road, you also have the option of letting it go back home on it's own...
But that's not something I suggest, especially after what happened to my cat - know what I mean :)

That is a tough question. I think I would snap the other end of my double ended leash on the other dog's collar and wonder around the neighborhood a little. Not sure how that would work with some dogs. I would see securing the dog out of traffic as the highest priority.

I usually like to see stray dogs turned over to the animal control. That is the first place owners looking for a lost dog will check. They also have chip scanners. They have secure places to keep dogs without endangering your own dogs or annoying neighbors.

I will admit that I was concerned in this case because the only information on the dog's tag was a name and phone number, which didn't have a local area code. (I looked it up on line later, and turned out to be a southern Washington state one.) I was worried that someone had either just moved, or come out for a visit, and this dog had gotten loose in entirely strange territory. Of course, it's possible that the owner has lived here for a long time and just kept a cell-phone number from Washington.

Which leads me to think that most useful information that should be on a dog's tag is a phone number and a street address with zip code. No need for city/state (the zip code will pinpoint the location), and really, the dog's name is nice, but not as important as where it belongs!