I might humbly suggest that this is why preamps are a rather pointless item for recording loud rock shows stealth with lavalier-type mics. The M10 is a quiet deck. You'd have gotten fine levels using a simple battery box and running line-in, and you'd have had one less knob to fiddle with and a smaller second box to deal with. You were obviously stealthing, so why make life harder on yourself for some minimal (if any) benefit from using an outboard preamp to provide gain? Oh, and the preamp probably goes through 9V batteries more quickly than a simple Sound Pros or Church battery box, which can last for months and months.
For that matter, when I stealthed with DPA 4021s, which it's fair to say are a bit more sensitive and nuanced sound-wise (and dramatically more expensive) than SP-CMC-8s, I don't think there was much if any difference going DPA 4021>some kind of preamp>M10 or R-44 vs. DPA 4021>48V phantom battery box>M10. In fact, the best single stealth recording I did with that rig was with the latter. I made a lot of nice tapes with SP-CMC-8s with a simple battery box, too.
I realize this won't help you fix what's already happened, and it's a bummer that you lost this recording, but I'd at least consider taking this advice to heart for future shows. Best of luck on your next one.