The BIOS does not see the hard drive. What happened to the hard drive?

Question

linux

On a laptop, on the same physical disk, they exist in parallel to each other: windows 10 (ntfs) / ubuntu (ext4) / elementary os freya (ext4), where each OS is installed on its own logical disk.
I reinstalled elementary os freya to elementary os loki by formatting the drive to ext4.
After a successful installation, I started setting up and installing the software. While working, I needed to restore files on the laptop's hard drive, for this I used r-studio. After restoring the files, I continued to install the software and configure the system (system settings are not significant).
At the end of the work, I rebooted the system, and surprisingly the BIOS stopped seeing the hard drive. Or rather, in BOOT Options it became empty.
Starting from a flash drive, with elementary os freya preinstalled, I checked the see-lt OS hard drive, the answer is YES.
It's like the start pointer of the hard drive was knocked down during data recovery, or, well, something else went wrong.
In general, what to do? And what could cause the invisible state of the hard disk for BIOS'A (where to dig in search of an answer)?

Answer 1

Difficult case. Try to restore the boot sector from under win pe. If it does not help, re-roll any of the systems that you least feel sorry for from a flash drive. And then from under the system try to restore another bootloader.

Answer 2

1. Make a backup of the necessary data.
2. Delete the first disk partition.
3. Put the correct bootloader in the first section.
4. Configure the bootloader, if required.
5. Restore data if required.