We travel a fair amount. We carry on masks, regs, computers, camera gear. Despite discussions here about strategies to carry on all gear, I meet lots of people traveling and this seems pretty rare. Not to mention impossible on many itineraries because of airline rules or small planes. (I did see my first dive caddy in Honduras a couple weeks ago and as packed there's no way it was within standard US carrier size limits.) It's also rare that I've met divers who have actually lost luggage. Not to say it can't happen but I think people lose way too much sleep about this.
Many liveaboards do have gear available and hopefully you'll hear from yours soon what their deal is. Sometimes it's on board, sometimes more if they can get it onboard before sailing. They should be prepared as they do have the occasional person needing it for some reason, including the possibility of a bag getting lost or delayed. And sometimes they'll even have a backup plan to get luggage that shows up next day to the boat, if the route allows.
Don's thought about arriving a day ahead for a liveaboard is not a bad idea, not only to give you the warm fuzzies about your luggage, but as a way to extend a trip a bit and arrive rested rather than frazzled. We've started doing this when it makes sense.
For the record I've lost luggage twice - and I'm still not losing sleep about it. Once on the way connecting through Barbados, the airport was under construction and disorganized at the time and I was half expecting it. We got it back the next morning. The other time on the way home from Curacao when we were unexpectedly put on a regional plane and they didn't send half the luggage (we had lots of company.) Was delivered to our home the next night, covered in animal hair with tags from a strange airport (thanks American.)
There are strategies to give your luggage the best chance. No dangling straps. Good luggage tags with full itineraries inside and outside the bag. Do something to your luggage to make it not look like every other bag. And keep an eye out when your luggage is checked to make sure it actually gets the right tags and gets safely on the belt, in the right pile, or whatever - I've seen some real disorganization behind the counter.