
Sounds just like my rott X GSD when I bought her home. The mum was pure rott (as Opi should be, so we were told), and they ahd her and her four pups in a small, totally enclosed horse trailer in the middle of the August 2003 heatwave. Opi was handed to us with wet forelegs where she'd been standing in the water bucket to cool off - took me months to get her out of that habit. Also, the sire (who they did actually own) had been rather conveniently taken out for the day - we now know it's because he's half GSD. Same reason they weren't docked, though we got the "it's illegal now" spiel for that. Opi was flea infested as well, and horribly underweight - the owner (a horse farmer) was worming her with horse wormers, and feeding the entire litter dry cat food.
Like you, we should have walked away but I just couldn't leave her there, and I don't regret it - she's one in a million :) and although I remember seeing rotts advertised from the same area previously (about the time of the mum's last season, I suspect) I've not seen any since, so hopefully they've learnt from it.
Good on you for getting lil pup out of that horrible situation, and I hope he brings your friend years of lunacy like my girl :D hopefully less affectionate toothmarks though!!!