Just to follow up on this.
I did try rejoining the orphaned drive to the cracked array. The snap server returned an error -4 and refused to do it.
I also tried splitting the array into separate drives and rejoining them again. This gave me a error -3.
Finally I gave up and recreated the entire thing with 100% data loss.
This makes me a sad panda, but I will recover. I'm not running a business here, nor do I have files worth any real money stored. It was mostly just data files (MP3, audio/video, images, etc) and archived downloaded stuff from the internet (torrents, et al).
I did check the log to see what predicated this entire fiasco. At some point, the server went into panic mode. When it restarted, the array had a partially truncated inode and failed fsck with an error 33. At this point the array was completely unusable and would not come up in degraded mode.
I pulled IDE2 (since I was under the impression that was the failed drive) but the array still did not come up. I put IDE2 back into the machine and pulled IDE1. This was my fatal mistake, resulting in one orphan and one failed array.
In short it was my own damn fault for not being more methodical about this.