How did it play when you tested it? And did you test it vs. Haven, Courtyard, Gear, and other 'save for later' cards?
I say this because on the whole Granary seems weaker than Haven. Haven lets you save a terminal for a later hand, similar to Granary, but on the other hand you don't have to wait until another Haven comes up to use the saved card. And two Granaries in the same turn seems like a waste of hand space.
Maybe this would be stronger if Granary could play the card from the Granary mat, instead of simply returning the card to your hand.