Big RAID 0 arrays should only be used if you have a cast-iron backup plan in place because you can guarantee that they WILL fail eventually.
That being said, if there are non-RAID drives in there then one may have simply encountered a bad sector and fallen out of the drive pool. There may be a way to get the controller to accept the drive again, at least temporarily. The next best option would be to try pulling each drive and cloning it onto a brand new replacement, but I have no idea if the controller will accept the cloned drive in this case (different serial number, for starters). There are various data recovery tools you could try, but again you need to clone the data onto new drives first.
If in doubt, especially if its mission-critical data, call in the professionals. If not, you just learned a very valuable lesson - have a backup plan.