How to reverse Locust ability (Aloc)

for some reason after adding then removing the locust ability from a unit , i can no longer select it, even after i remove it.

is there a work-around?

There is no way to get rid completelly of them, but you can hide the unit, and show the unit, that will at least make it selectable again, but the unit's name won't appear when you hover the mouse cursor over it