Since there was a distinctive sensitive spot and John wasn't in any need to hear the information he wouldn't press forward. He could be something of a bastard sometimes in order to get things. How a kid got another arm, well, he'd be able to sleep that night without knowing.
"Good for you, mate." Kicking back the rest of his drink down the hatch John decided it was time to call it a night and go take care of his brother's widowed dog. She was probably a right mess sitting there all alone with her separation anxiety. He made sure to pay for his tab and then...well, because he could, he set out a cigarette on the bar counter for the kid.
He wasn't going to drop dead that night for being nice to a random sod who brought up conversation. Lord knew he probably needed it. "I've gotta class to teach tomorrow, I should be going. Don't get caught yeah?" More importantly don't tell the University he was giving out cigarettes and drinking with possible students. Shrugging on his jacket John exited the bar to hopefully be on to crash right to sleep. Hopefully.