How Peter Pettigrew came to live with the Weasley's

I think many people forget that Scabbers was once Percy's pet rat. It's never fully explained how Percy came to possess him, and I can't imagine Wormtail would have chosen to go into a wizard's pet store. After all, he had been in the family for twelve years, it seems more likely Percy would've stumbled on him accidentally and heaven knows how far Peter's house was from the Burrow.