I have done the same and have not received a response either. I recently emailed RAGBRAI a question and it took over a week to get a reply. That is not their normal response time and in their response they apologized and said they are swamped with email and other work right now. I have to say that I believe them and I am willing to be patient.

BTW, I decided to transfer my registration to next year, if anyone cares.

I thought the same thing, but then I went back and re-read the email from RAGBRAI that provided the details of the transfer process. The email DID state that confirmation would be sent in June. Therefore, at this point I will wait until June to see if I get the confirmation before bothering them again.