First of all, don't freak out. I don't have a lost dog.
The 21st century has blessed us with many high-tech ways to help reunite us with wayward dogs, from GPS tracking collars to implanted microchips to smartphones that allow us to receive calls from good samaritans who might've found a lost dog and pulled a number from a collar.
It reminded me that I also have a rather 19th-century technique of finding a lost dog: a wanted poster. After losing a dog two years ago in Montana, it struck me that we had no photos or other ways to quickly inform people that we had a dog missing.
I believe that the large majority of folks will keep an eye out for a missing dog if they know about one. I also happen to think that the sooner you can get the word out to nearby gas stations, cafes, motels, and post offices, the more likely it is that someone's going to stumble across your missing hunting buddy.
I've printed out these flyers for all three of my pups and have them (along with a thumbdrive carrying digital versions) stashed in my truck. There's room to put specific information on the poster, and I've printed them in color, for more accurate identification. I put my two phone numbers (anonymized in this online version, of course) as a tear-off along the bottom. I figure a rancher might see my dog while driving along a country road, and they'll be more likely to at least report the sighting to me if they have my number close at hand.
God willing, I'll never have to use them, but I feel better knowing I've got them.