I had the similar issue but after an update with pacman -Syu in the background funnily enough i had been using adb with a device prior although i don’t believe it was related to my issue.
Whilst it was updating it moved on to upgrading packages, unfortunately it seemed to hang while updating Virtualbox, it was stuck upgrading this packages for about 15 mins, i assumed there must have been a problem, not acknowledging that it had also yet to update the kernel i used ctrl+c interrupt signal and then rebooted.
At this point it would not boot past the boot loader as it would say the same error message that the kernel was not present or unable to find kernel image. I checked the grub boot script using e but it was showing a boot script, so i chrooted using a bootable USB archlinux installation and continued with pacman -Syu to finish upgrade rest of packages then used grub-mkconfig -o /boot/grub/grub.cfg then i found out that manjaro has update-grub command which i could have used lol. All jokes aside now my grub script did not show any instructions to boot 
. Long story short i noticed the kernel image in /boot had a .kver extension and /etc/mkinitcpio.d/ did not show my kernel version although 2 others that i was running before i was running the current one. My suspicions that it was a kernel issue anyway as was expecting to see vmlinuz on its own in /boot not with that extension that i haven’t seen before plus at least an initramfs.img image but neither was present only the one with .kver extension, as i was originally trying to boot from grub command line but couldn’t find the files.
I ran mhwd-kernel -i linux515 whilst i was chrooted in the filesystem all outputed the same error message so tried all the different versions until linux66 which did seem to work and asked me to confirm installation, and rebooted.
I could now see a populated boot script using grub E command from Manjaro grub splash screen with the kernel version linux66 option showing to boot from. Failing this would have tried installing a new kernel via pacman.
following this link also helped
I Hope my experience with this situation could be of use to someone.