I swear the first time I booted I saw it - and i tried to configure it to be the cache drive but something weird happened (I don't think the array was up yet, i hadn't even added disks to it). Anyway, I can't even find it in lspci or nvme. I've attached my diagnostics zip file. The NVME drive manufacturer is micron, MCRN 2200, 1TB M.2 NVME CK1AT1AABYY.
mustard-chief-diagnostics-20200915-0932.zip