Scotch Bonnett,
The "claw back" goes further than that....I know of one individual who left the AAC in 2005 for service in another arm, who is being looked at, not only by the AAC.....but for the knock on overpayment from his present service.
I think that you would need that statement in writing and dated before you could begin to use that.
I imagine you would have had to have formally expressed your thoughts on paper (how many of us do) to claim retrospectively.......or we could all do it!