Nonoccurring

A dinner given merely to enjoy the pleasure of entertaining one’s friends is a rare, if not nonoccurring, spectacle.

Vandalism becomes virtually nonoccurring, except during vacations (which should tell us something about some students’ needs to be involved).

The other possibility is to give -ation a unique analysis as -ate + ion and to allow morphology to produce *documentate as a possible but nonoccurring word (perhaps blocked by the verb document).