Would the Enigma Archetype mesmerist be able to use lock gaze before using his stare to lock a target into staring at a target it cannot see? Or would that not work because you would become invisible to the target?
Rules aside... how does one "stare" at something that cannot be seen?
That said, there just isn't any rule for what happens when targets (or in this case sources) of spells cease to be valid after the spell has been cast. So ask your GM.
But be prepared to be ridiculed. ;)