nanny2507...............you may have already answered this somewhere, so apologies if you have. Have you tried:
contacting all the vets nearby (say a 5 mile radius?
ringing PDSA, RSPCA, any other animal shelters?
Putting up posters with a description and photo?
Placing an advertisement in your local newspaper?
I did all of those things when one of mine went missing. I printed off posters, put them in every door on my street and the next road, as well as the local shops. I laminated some, tied them to various lampposts. I did so many things to find her...... and she strolled in at 3 am one day, all thin and wet. She didn't venture far again.