[panick21_]

You just go to distributed launch. You launch a rocket multiple times, fuel up and use that to escape. If you use your upper stage as the primary, its unlikely to ever come back.

But in future you would potentially have special boost stage for that. See something like Impulse Space is building.

But for these really powerful throws, its probably just cheaper to just drop an upper stage. Upper stages are a drop in the bucket compared to the cost of a flagship mission. A Falcon 9 upper stage is only a couple million $.