When we're going for Senior, in both dinghy and keelboat, we're quizzed on how we would deal with rig failure, a shroud or even worse a forestay. We know the answers, and we carry line and maybe shackles to jerry-rig something, and we think about the extra lines we can use, especially on the keelboats where there are multiple halyards, topping lifts, and the rest.
But it's one thing to "know" how to deal with it, and completely another to deal with it when it happens.
I was doing a dinghy qualifying cruise to Treasure Island under Mark Playsted's supervision. Not a difficult cruise, beat out, run back. It was blowing pretty hard, gusts into the twenties, forecast for higher. We had two Ventures with 3 people in each, which worked out well with one person on the wire a lot of the time going out.
We were almost to Treasure Island when it happened. I saw Mark on the wire in the other boat go into the water, then I saw the mast at maybe 20 degrees off the vertical. It was clear that they had lost their forestay, and I thought the mast was next. But it wasn't. They were holding the mast up by hand and getting the mainsail down. Within about 15 minutes, Mark had rigged the auxiliary stay to the bow and the boat could sail. They made it back under main and gennaker, and BTW the gennaker took a lot of the load that the missing forestay would have.
It could have been my boat, and I don't think it would have come out so well if it had been. I'm thinking dismasted here. It was great to see how this could be handled, if you do all of the right things quickly....