Also, at this point, don't count on getting any replies. It's the weekend, folks. Wait until Monday, see if we get an official announcement or something. Like Lord Seth said, write your letter, wait a bit, and go back and read it.
And like others have said, this may not have been knee-jerk on their part; there may be issues with other larger potential donors. Still sad, but at some point, you have to look at hard numbers.