Putting up posters is a good idea. If you do not have a good picture of her, use a Jack Russell breed picture. You just want to give people an idea of what she looks like. Let your newspaper carrier know that she is missing. Check with area vets. If she is still on the loose, she may find food in the back yards of other pet owners. If you walk her in the neighborhood, she may be in the area of your walk. Hopefully a kind person has let her in, is feeding her, and is waiting for the owner to find her. Just keep knocking on doors. May an ad in the lost/found pet section. Good Luck....our prayers are with you.
"I have not failed. I've just found 10,000 ways that won't work." --- Thomas Edison