amzie no sure if this is an old wifes tale but i was always told that if you rubbed butter on a cats paws, before letting it out in a new place that it would find its way back, and strange as this may seem it tended to work for me when i moved and let my cat out, she didnt stray very far for a few weeks, but did come in when she was ready, hope this helps. also i would maybe try and keep the other cat in the first couple o times you let yours out just incase it chases it away!