Hi, I'm not sure what exactly caused this in your situation. It was interesting to me, too. You are right as a single drive can be run as RAID0. In general, there are possibilities to tolerate faulty disks for sustainability against possible disk failures in RAID configurations(except RAID0).  But I should say that it would be better not to substitute RAID structures for redundancy. I mean, we shouldn't rely heavily on RAID for data redundancy. It may be better to think that RAIDs are necessary for the system to work a little more securely by being able to tolerate possible disk failures(which is not 100% even at such moments). 
I have a R710 server with RAID1 with two drives for OS (Windows Server 2012, RAID5 for database data and two RAID0 drives one of which was holding DB backups and the other one was for Windows backups. Lately one if the RAID0 (dbbackups) drives failed and now both disks are showing as a one single virtual drive in RAID0. Both drives are not showing in Windows anymore and while I have not lost anything yet, Is there any way to recover the good RAID0 drive?   Obviously nothing is lost yet, but I am a little frustrated with this setup and the outcome of the drive failure. The only operation I can practically do now is to delete the virtual disk which will probably delete all Windows backups with it. The controller is PERC H710 mini
Two drives set up as RAID0 - are both of them lost after one of them failed