According to the article, the guy left with the boat tried to right it to go pick up the man overboard. Do this as a last resort, and only if you are confident you can do it and manage the boat afterwards by yourself.

If a crew is swimming to catch up with a capsized cat but not fast enough the correct action is to turtle the damn thing ASAP. With the sail down in the water as a floating anchor and the trampoline no longer acting as a sail the boat will drift at a slower pace and the swimmer will have a better chance to catch up. Anything to slow down the drift even more is good, paddling, pulling the spi out of its chute in the water, sheet in the main (now underwater) hard...