UEFI is a strange beast to me but recently bought myself a new laptop, a Lenovo Y50-70. After getting dual-boot working fine for a few days, Debian disappeared from the EFI boot menu and grub no longer booted. This looks like an issue with a corrupt EFI partition. This is how i fixed it.
This caused me a major headache when i first setup my laptop, I wasnt aware this could cause a problem. After quite a lot of messing around and a lot of googling, this is what i came up with. This was a known issue.
It is possible the windows “Fast boot” setting has caused this. It is advisable to disable that. The option for that is in power options in Windows 8.
Boot laptop using Debian disk.</p>
Select advanced recovery</p>
Mount the Debian partition and start the shell on that partition.</p>
Mount your EFI parttion.</p>
NOTE: Mine was /dev/sda2</p>
root@jon-debian-laptop:~# mkdir /mnt/sda2
Now we run dosfsck until no error appear. I had to run it several times.
root@jon-debian-laptop:~# dosfsck -r /dev/sda2
(Repeat multiple times, until you get the following)</p>
root@jon-debian-laptop:~# dosfsck -r /dev/sda2 Dosfsck 3.0.13, 30 Jun 2012, FAT32, LFN /dev/sda2: 325 files, 12146/65536 clusters root@jon-debian-laptop:~#
After that, i reinstalled Grub. That may not be needed, but i did so anyway.
Here are the instructions: Here