
My sister has the problem with her boxer bitch. She is walked on a retractble lead now, because she just wants to play with everything in sight & will go 'deaf' when she doesn't want to go back on her lead. Boxers have so much energy, it seems to be a catch-22 situation - the less off-lead exercise they get the more energy the have to burn off & the less inclined to return to owners.
Sorry if this is too much of a generalisation, I'm only going on my sisters Boxer behaviour, she could go on a 10 mile run & still have too much energy to agree to returning to go on her lead, she is a very stubborn, very inteligent, very energetic bitch, who despite looking like a very rough dog (she's white with 1 eye) is the biggest softie you could meet.
You are right, any negative behaviour/reprimand when she is caught/does return will only enforce her not wanting to come back. Hitting a dog does nothing to train it, it's cruel (IMO) and leads to lack of trust & confusion - the dog comes back, gets a wallop, why would it come back out of choice the next time?
I would suggest making sure she has some mental & physical exercise at home, before going on her walk in an attempt to burn of some of that pent up energy. In the mean time keeping her on a long line/retractable lead and practising her recal. My sisters Boxer is more likely to return when called if there is a fun game as a reward, treats just don't do it for her.
I'm sure somebody with experience with Boxers could offer much better advice.
I must add that I can't get over my sisters Boxer's intelligence, she can take the lid off a drinks bottle by holding the lid in her mouth and twisting the bottle in her paws, she will then tip the bottle up & have a drink!!!!!! (makes it very easy giving her water on a long walk), she also can open doors inwards, by pushing the handle down & pulling it towards her & has opened the garden gate to escape, that intailed lifting & holding the catch up with 1 paw, while pulling the gate towards her with the other paw!!! Gosh, my poor doofus of a Mastiff can only open a door that is ajar by headbutting it :(
ETA sorry, I've reffered to your friends male Boxer as 'she', sorry :(