Any activated ability that I've been able to test and try does not return quantum if you cancel it's use. In addition, if you cancel the ability, it will be "locked" as if it was used that turn. Essentially from what I've found, activated abilities when cancelled are not really cancelled, just not given a target.
I did not see this in "Confirmed Bugs" or "Not a Bug" so I'm not sure what to think of it.