I have a dual-boot Ubuntu 16.04 alongside windows 10. I just restarted the system and stepped out for a while just to find out on coming back that the system was showing me the BIOS screen. In the boot menu it shows two boot options Windows and Ubuntu for both of which it has (Drive not present) . But when I tried to install windows 10 with USBFlash drive, i thought of going to repair option and went to command line to check if files are present. Fortunately all my files are still displayed in the command prompt and i took a backup of few files from windows, but couldn't access ubuntu partition. Keep in mind that i did not install windows again, i just took a backup using the command line.
I am almost having a nervous breakdown, almost most of my work is there in my laptop(ASUS X550C). Not able to boot into either of the Operating system.