Tomatoes are vines- they grow from the ends so don’t cut them off. What he can do if he wants to is bury part of the stem so the green part is sticking out of the ground like a new plant but leave it attached to the original plant until it grows new roots from the buried part of the stem. Then, after a month or so when new growth is apparent, cut it from the mail stem. I do this every year in Fall pto prolong my season here in So Cal. Whether it will make it until Spring depends on where in SoCal he lives and if it gets frosts there.
