I wouldn't say there's no way back.
ETH has always been pretty straight, follow the rules and you'll be considered. The state of our injuries/suspensions/random legal issues suggest opportunities will arrive - if he'd apologised he'd probably have been playing on Saturday
The question is whether or not Sancho is prepared to fall in line and just how stubborn/childish is he prepared to be. The squad has a role to play here, a strong dressing room should be letting him know it's unacceptable over and above what the manager does, Sancho needs to know he's letting his teammates down, he should be ashamed of that.
Training alone can get real boring real quickly, I imagine he'll be back in contention soon