Hard drive bootloader doesn’t see High Sierra, but the USB one does?

I’m using a Lenovo Y70, which has essentially the same components of the Y50 in a bigger case.

I created a High Sierra USB installer with Unibeast, then got it installed (APFS conversion was disabled). It works perfectly once booted. When the install was completed, I downloaded Clover and installed it in accordance with this guide.

I then rebooted, and was welcomed by the Clover screen, but with no option to boot High Sierra. The only option is to open the Clover Shell. I plugged my Unibeast USB in and its bootloader was able to see and boot High Sierra from my hard drive.

I know the issue is in my hard drive’s bootloader, but I don’t understand why. Where did I go wrong, and how can I get it right?