Maybe put up flyers in both your new and old neighbourhood (in case she walked back there). Also contact local vets and RSPCA or similar. My friend once lost her kitty (microchipped and all) she called the RSPCA who found the cat, but didn't bother to contact her. It was about an hour drive away, so she told the RSPCA to hold her kitty until my she would get there. My friend jumped straight in the car and raced over there, but by the time she got there THEY'D ALREADY SOLD THE CAT (I know - WTF!!). They earased the data on the microchip and all. So please, please call around, they don't always contact you! And be determined - if they have your cat don't let them take it. I don't mean to scare you, but I thought you should now that.
Again, I wish you all the best.

PS: They had the cheek to charge the new owner for 'microchipping and vaccination fees' - but it was my friend who paid for that - not the RSPCA.