Stop prompting to unlock disk
Instead of using UUID try using LABEL. This will help to rule out UUID problems.

The following line in /private/etc/fstab stops the drive named SpareSSHD from mounting on OS X 10.10:

LABEL=SpareSSHD none    hfs rw,noauto


My drives are encrypted with FileVault2 and this works.

The following links provide more detail:


How can I tell OSX NOT to mount some of the drives in my computer?
fstab(5) manual


/private/etc/fstab and /etc/fstab are the same file. As @forquare confirms, they are symlinked. You can edit either.