A "Comeback"

...is Crappy Tire shop-talk for a customer who gets home and finds out the car problem he or she just spent $100s on is still not fixed.  And so here I sit outside of Crappy Tire, a hard-won day off in ruins.

A "run right back" is a customer who realizes even before he gets out of the lot--maybe his engine catches fire--that he's still leaking gas or whatever.  These can be especially embarrassing for service centre staff when its closing time and the mechanic has gone home.

So there you have it.