I don't know about a bell on her collar, but a beeper like on the wireless phone might be handy.
Bentley did that yesterday. He's been staying since Monday and during the day yesterday, Miss 18 got a call to go to work. Bentley has discovered the wide outdoors and being in a cul de sac and a quiet area anyway he's often roaming around ours, Mikes, Sarah or Rods. All good. But yesterday he would not answer her. He would not come. She had to leave for work at 2 and I got the hysterical call "Bentley's missing..... I caaaaan't *sob* find him *sob*"
Master DT looked from 4 until 5.30 when he had to go to work
Mr DT looked from 6 till 7.30
I got home at 7.30 and yelled "Bentley, ya little shit" and he popped up saying "meh?"
Dear wee man - where was he?
Sounds like little Mr B knows not to mess with Grandma