If you mean Spam F8 to see the devices, I couldn't see the SM 951 prior to installing W8.1 Pro. I flashed to 1502 via USB (FlashBack?) before even mounting the CPU/RAM.
It is a fresh build - RVE w/1502, SM 951 M.2, W8.1 Pro. My first M.2 drive, first UEFI OS install, heck, first ASUS board. I could never see anything to indicate the SM 951 even existed in the system and couldn't get my DVD drive to show up as UEFI (and honestly never really figured if it was supposed to be, but Chino's guide seemed to indicate it was a possibility). I wondered if the M.2 drive was bricked or not seated, but figured I'd pop an OS at it and see what happened.
So I made a bootable USB stick and it had no problem picking that up as a UEFI option, but it wasn't until Windows was installing that I saw a destination - Drive 0 I think it was. After getting the OS installed, the SM 951 is now C: just like you'd expect, and it shows up in the F8 list. I had little confidence until I saw Windows was installing someplace and there was only one drive mounted.
Not sure if this is the issue the OP was having, but I went ahead and installed an OS without ever seeing any drives in my system. And it seems to be working fine.