Spot the frisbee

Spot the frisbee I’m waiting to catch, by leaving a letter/number comment and win a special prize. The frisbee has been digitally removed by a hoard of rare golden photoshop monkeys.

NB: Special prize may be one of three dead Bonsai threes. Or a half eaten book on how to keep Bonsai trees alive.

UPDATE:
Ok, here the original image.

The answer was D16. Thanks for playing! Alex was the closest with D17. I’ll put you down for an IOU pint.