This happened to me a couple of years ago but as we, at least in the NE, start to get ready to launch, it might be worth checking.
I went out to my boat (on a mooring) one sunny day and found the forward end of the boom had fallen out of the gooseneck. It was held up at the stern by the topping lift.
A quick inspection revealed that the clevis pin had worked it's way out allowing the boom to disengage. The oddity of this is that, unlike normal clevis pins that have a hole at one end to allow a cotter pin to be inserted, mine did not. Instead, there is a vertical hole in the top of the gooseneck thru which a pin was inserted (see picture). This pin went into a hole in the middle of the clevis pin. This pin must have sheared from stress and broken, allowing the clevis pin to wiggle free from the movement of the boom while on the mooring.
Luckily the forward end of the boom fell into the vang rigging or it could have gouged up the deck. It could have been disastrous if it had happened while under sail. A normal clevis pin and cotter ring solved the problem.
I have had cotter rings come loose on other parts of my running gear so captains might want to check all points that have clevis pins and change out the gooseneck clevis pin if you have what I had.
HelenRita 2072 Mk II
2002 Tall Rig - Winged Keel
Atlantic Highlands, NJ