We lost our shih-tzu? =(?

we lost our shih-tzu this saturday. she was a puppy mill rescue, we lost her the day we adopted her. long and stupid story, worst day ever. we still havent found her yet. she doesnt know the area and barely knows her name. we dont know where she went but we've been scowering the area for days now. called all humane societies, the police, informed people we see along the street, informed her fosters, put up online ads, been driving and walking around for several hours a day. we have put up flyers everywhere, the grocery store, community centers, the neighborhoods that she most likely slipped in to, the veternarians office, a lot of the bus stops, almost everywhere we could think of.

today was day 3 and its over and still no results, it gets really cold at night around here too =( shes shy and still doesnt trust people yet, but she would never bite.

does anyone else have any other ideas on what we can do? and what are the chances that someone found her and decides to keep her, what are the chances she didnt make it? what else is left to do other than keep searching and checking the humane societies?
my family and i are really getting desperate
yes she is microchipped.
however she isnt wearing a collar or harness.
shes also spayed
however the microchip is still under the name of the humane society we adopted her from, since we just got her and havent had the chance to change the information yet.
thank you.

we did contact her fosters. she couldnt have gone back to the puppy mill, she was one of the dogs from the tennessee puppy mill case, the one with over 700 dogs. she was never happy there. if anything shes trying to find her fosters. and thats over in virginia, she doesnt know the way =(
uhm to the person who wanted the long story. sure you can have it.

well, we brought her home, as i said shes a puppy mill dog and was previously with her foster of 2.5 months, we brought her home, she seemed a little nervous but we could tell she was settling. actually one of our neighbors, some guy from the home owners association came over and did the entire "knock and open the door" method so as soon as he opened the door he bolted. WE didnt open the door, we didnt even want him over anyways, he just came. he was unwelcome. but either way, she bolted my dad chased her about 2 miles non-stop to a nearby gastation at a major intersection, she ran across the road, luckily there were not many cars though, and my dad finally lost her. my mom tried following in the car, my brother searched through the woods. i wasnt there, i was actually away and i didnt find out until a couple hours after it happened when i got back home. none of us wanted it to happen
no ones saying this isnt our fault, yes it is, we should have been more cautious of the door, my mom was keeping an eye on her, but from a distance. shes our second shih-tzu, and this is the first time something like this has ever happened.

Where were you when you lost her?
I stopped at the store one time with my little dachshund and I needed to run in for only a moment to pick up just a couple of things. It was fall, it was not cold but not hot. I left both windows cracked in the front, locked the door and went inside. I wasn't in there for 10 minutes, but when I came out he was gone. I panicked, looked everywhere,asked every one. I went inside the store and asked loss prevention to review the tape from the area of the lot I was parked and they did. They seen a lady carrying him around the parking lot, but never could trace her back to her car.
I did everything you are doing, but I decided to go back to the store where we lost him and put up signs at all entrances hoping whoever picked him up would come back and see. Exactly one week later I received a call from an animal hospital that had him for 6 days at that point. Apparently I had left the window down too far, he jumped out and this woman had seen him and took him home for one night and the next day took him to this facility. She went back to the store the following Wed., 7 days after she found him and seen the sign. She called the place she took him to and they called me.
I had lost all hope that we would see him again, but I was persistent at doing everything I could to get him back and it worked.
I would call every animal shelter/hosp. in the area and let them know that you have lost your little dog so they are aware if one is brought in. I am so sorry,I know what you're going through. I wish you all the luck in the world.