How is it possible you can't undo an station ability? I tried to use my Nanoform Sentinel to untap a land while station but I forgot to tap the land first. So I thought with 'z' just will be back to prior state of the match, but no, and that was crucial on losing that match. Intuitively, if it is possible to undo the tap of the land, one expect to undo the tap of a stationing creature.