I have a laptop that I installed Arch on, so far so good. After getting things set up just the way I wanted them and using it for a few days, I decided to experiment a little and install SteamOS. Since I didn't want to mess up my Arch install, and I happened to have a spare 2.5" drive flying around, I just popped the old drive out and put the blank one in. After playing around with SteamOS for a while I swapped the drives back, but now Arch won't boot.
I did not change any BIOS settings. Entering the UEFI boot device selection does not show the HD with Arch installed unless there is another bootable device present (a flash drive with the arch install media in my case), in which case you can manually select the EFI file for GRUB on the HD and boot into Arch normally.
Why would swapping drives suddenly render the old drive unbootable? How do I repair it?
EDIT: After doing the USB stick hack to make the UEFI let me select a file to boot manually,
efibootmgr reports the following:
BootCurrent: 003D Timeout: 0 seconds BootOrder: 2001,2002,2003 Boot0000* USB Hard Drive (UEFI) - SanDisk Cruzer Boot2001* USB Drive (UEFI) Boot2002* Internal CD/DVD ROM Drive (UEFI) Boot3000* Internal Hard Disk or Solid State Disk Boot3001* Internal Hard Disk or Solid State Disk Boot3002* Internal Hard Disk or Solid State Disk Boot3003* Internal Hard Disk or Solid State Disk
For obvious reasons I can't show the output without the USB hack. The UEFI manger (accessed by pressing F9 during boot in my case) simply does not show the HD as an option unless there is another bootable device available.