Glad to hear that your mother is ok, and I hope you're able to find Leslie.
A tip I've heard when a dog goes missing is to include two things on the LOST DOG flyers - first, that there is a cash reward (don't specify how much though), and second, that the dog needs medication. Some people will take dogs, especially small dogs, even if they know they are lost and belong to someone else. But if they think that the dog is going to cost them a lot of money in vet bills or will be sick without its medication, they are more likely to give the dog back. I have this information on all of my dogs' tags as well ("needs medication - reward if found").
Be sure to post ads on as many sites online as possible. Off the top of my head there's Craigslist, Petfinder.com (they have a free section for Lost/Found ads), fidofinder.com, amberpetalert.com, lostdogdatabase.com, missingpets.com - just do a google search. Also contact the local shelters and rescue groups in your area - some of them might also have websites with a lost/found section that you can post on. Make sure to take flyers to all the local pet stores, groomers, and vet clinics as well as the shelters, and of course any non-pet related places that you can post them too (supermarkets, gas stations, churches, community centers, etc).
My and my ex-husband's dog was missing for two weeks once but I was able to find him. Don't give up hope!