7 days?? darn. If that was my dog who was lost and I couldn't find him after 7 days I would have trouble with allowing someone else to keep him. Please do continue your search...I would hate to think there was some family out there in distress looking for him. I know you mean well but you can never be sure of the circumstances of his escape. He may have escaped innocently, he may have been dumped, he may have chewed through a tie out. You just never know.