I've worked with vBulletin forums since, well, there was vBulletin and the simple reality is that databases get corrupt when there's high levels of concurrent usage. While I won't go down the technology argument too far this is more common with generic scripts like vB which have to cater to a wide range of hosting platforms than what you'd see if you built your own system ground up. Generally this can be fixed, sometimes with just a few queries, sometimes with hours of digging.
As for your circumstance you may not like what I'm saying but it's going to be on you to get this fixed.
Basically you have providers tasked with parts of the equation but no one in your scenario is responsible for your site.... Your hosting company provides hardware and bandwidth but unless that crashed and caused the issue, it's not on them to have any involvement with what you install, even if they try to get involved when they can. Then you have a piece of software that comes with install help and bug support but again is no fully managed system -- their line (and what lets them make the licensing fee be so low) stops at functionality. Your technical admin is the only real possible person on the hook but if they've been hired to build and customize rather than manage and protect, that's a pass as well -- plus they don't know what the solve is.
What you're expecting is managed support and what you're paying for (from what you've explained) is scripts & servers. I realize you may look at the costs as expensive but having someone responsible is thousands of dollars a month on top of hardware whether things go wrong or not -- it's a common gap and frustrating but it is reality.
But more than who to blame, right now you need to be online. You have a serious painpoint and none of the other parties will feel it the same. The longer it takes to get back, the less people will return. So get your site back up, figure out what you think is fair but again, unless you're paying a very big bill for a fully managed solution to someone that you didn't mention, I doubt you'll see a nickel.
And moving forward don't assume your software or hosting covers your world. Things will break... someone hits delete, you get hacked, the database goes down again. Put the money in, get your site to a place where it backs its self up and where it checks and repairs corruption now.