Ubuntu – bios not recognize internal drive as bootable after disconnecting and connecting back in

I have a serious problem. I had a perfectly good working UBU 14.04 LTS on a 1TB WD Drive in SATA 1 position. I had a good and working Win10 installation on a Seagate 180GB HDD.

I turned off the computer, plugged in a Clonezilla Live USB, plugged in an external Toshiba USB 1TB Drive, and a WD 3 TB Drive.

Then I booted the computer to the Clonezilla flash drive, restored the WIN10 image from Toshiba drive to the WD drive.

I turned off the computer, unplugged every drive, plugged in my 1TB WD drive with Ubu 14.04 and I get a message that there is no bootable device available.

I look in the BIOS and the drive is there, it's the only one, but it doesn't show in the boot devices. Instead, it shows the words "hard drive".

Threads read that do not apply:

1. GRUB menu lost in win 8 dual boot configuration after hard drive swap
2. Boot menu does not offer choice between Ubuntu and Windows
3. Dual boot windows 8 (UEFI / GPT) with Ubuntu and boot-repair

I am booted to Live USB now, and gparted shows the drive with the following partitions:

/dev/sda1 fat32 {no mount point} Size: 380MiB used: 4.13MiB Unused: 357.87 MiB Flags: boot
/dev/sda2 ext4 {no mount point} Size: 22.84 GiB Used: 9.72 GiB Unused: 14.12 GiB {no flag}
/dev/sda4 {key} ext4 /media/bef01012-a316-4c2c-9d93-fc16b989ae62 Size: 407.30 GiB Used 99.97 GiB Unused: 307.33 GiB {no flag}
/dev/sda3 {key} linux-swap {no mount point} 7.81 GiB Used: - Unused: - {no flag}
unallocated unallocated {no mount point} Size 492.12 GiB {rest of line blank}

In my file system, I see 26GB Filesystem, 437GB filesystem, and Ubuntu 12.04.5 LTS amd64 (flash drive.)

I cannot mount the 26GB filesystem, or sda1, the fat32 partition.

I read the following "similar questions":

My BIOS has few settings that I can change compared to my laptop's BIOS. I have tried resetting factory defaults, turning on and off secure boot, moving the drive to different SATA ports (This computer only has two SATA connections and they are SATA II)

I disconnected them and installed the 3TB Win10 drive I sent the restore to and it booted and worked, in spite of it being for a different computer. I did a full shutdown, not a hybrid. I unplugged every drive from the computer, I tried setting BIOS defaults back to factory setting, and nothing seems to work.

Except for the Toshiba drive, these drives are all SATA internal.

… and many more.

===================== Additional Info ============

I have done some more experimenting with this to see what I can do.

@kos and @Ashhar Hasan

I removed all drives from the computer and rebooted to, hopefully, reset the BIOS.
Then I installed the drives as they were originally before using the computer to create a backup of my laptop drive.

It will only boot to windows.

@Old Fred

I'll see if I can repair the grub or boot loader after lunch. Thank you all for your answers.