Don't have proof, just never heard of this (the issue you are having) before and it sounds prepostrous. What I have heard, specifically in fact was as stated before, that eco credit is locked in at the time of order and is not related to the time of delivery. But, I plan to make sure my sales guy quadruple checks this info 1st thing tomorrow. He's been very straight w/me so far and seems very capable so I do not expect a run around. If this info exists he will tell me. OTOH, it may be impossible to prove it if this information is somehow bogus and/or specific to your dealer. Although I am not sure why your dealer would make something like that up - sounds farfetched for them to try to re-neg on a deal and get more $ or something.
I will try to get him to tell me how he knows whatever he tells me. A bulletin, web site, some other dealer info channel... whatever.
spacey