There is no cover mail option with applications to most schools. Your only option will be an optional essay used to explain a variety of items, which you are welcome to do. That is your only recourse at this time. (You can definitely try contacting GMAC but it is unlikely they would budge).
However, you will definitely be not the first person with such scores. Second, what about all other applicants who apparently were better at canceling their scores than you? While their records may look clean, Adcoms realize that they are not being presented with an accurate picture when someone submits a 710 and no other scores.
Also keep in mind that until about 2 years ago, it was not possible to cancel the score after seeing it, so millions of candidates have had multiple scores on their reports.
Again, if this is a concern, you definitely should use the optional essay space to explain this situation. Fairly straightforward. Takes 2-4 sentences and we both have written much more about it
P.S. Just to add to anyone thinking of taking a test cold and then canceling scores afterwards, some schools have decided to ask applicants to list all of their scores (canceled and not) on the application - Kellogg has done it this year, so be responsible when you decide to take, retake, etc the GMAT, and as a reminder, there is a 5 tests/year and 8-test lifetime limit.