I am very sorry to hear what happend to you Tina - i cant help but thinking was that something the owner planned on maybe ??
Maybe the pup is too young and maybe im seeing ghosts, but I heard about a similar story in Poland some years back, where people bought a Dobermann
I might be a bit too suspicious but, could the breeders as in the polish example,have taught the dog to run away - and only answer to their voices - and when they picked the dog up after the new owner gave up looking, then the "breeders"would either pressure the new owner for more money or sell him on to the next buyer
Hope this is not the case and that you find a solution - just only saying if thats whats going on then be carefull
FK