Weeks ago I accidentally broke off part of the stem of one of my tomato plants. I put it in a glass of water and it started growing roots, so I planted in a pot of its own.
Just when I thought it had pulled through, I broke it off again (accidentally, of course). Not sure how much abuse a little plant like that can take.
But at least its mother plant continued to grow fine.
Another one of my plants, that was already carrying small green fruit, I dropped from quite some height and the stem broke off completely. I doubt that a big plant like that can grow new roots quick enough to recover.