what would happen if a coaster didn't make it back to the station?

I once saw Mantis aaaalmost valley before the park opened one morning 2 seasons ago. I remember some other employees and I going "oooooooh!" and it baaarely made it over that hill. It was intense.
I know for Mantis that they can start the ride from the top of a later hill, because once I test rode halfway through the ride. We had to go up a spiral staircase and there were a bunch of employees that assisted us. The ride was significantly slower and some mechanics tried pushing our car to give it a running start. We almost valleyed once or twice but managed to get to the station.

It's just a job Rideman. :)

Most of the time, these rides (across all parks) are designed to make it around the circuit no questions asked empty and unloaded. Some coasters, a-la Gemini and Magnum, for one reason or another have a hard time doing so. I know from working Ride Pride, that Gemini had to have the ride filled with sandbags before opening to have the ride complete the circuit (of course with me sitting in the front seat for test rides, 17 consecutive trips on Sunday!).

I believe that the ride will stall at the final helix without weight in it and requires a crane to pull it back in to the station. I don't know if that is due to age, design or what. But I do know that it is a great disruption if such a thing happens. Which also is the reasoning behind them only going to one track when there is little or no line (I think). It also has manual brakes, so next time you are in line, look at the roof sway as the ride comes into the station. Especially if they are busy and don't pump them!