I found why my boot USB display 'Missing operating system' massage, use my surface tablet.
If I boot the laster ver. Remix OS installed in USB flash drive, it spit out like this.
error : no such device: /cm-x86-14.1-rc1/kernel
error : file '/cm-x86-14.1-rc1/kernel ' not found.
unaligned pointer 0x86870bf8
Aborted.
I tried to install on three different computers, but any installation isn't success.