I left it blank I believe, but I think they matched it to my existing account because the spending miles posted there. Am I out of luck?
Probably.
Arguing that they sent me an e-mail stating "Your 25,000 miles are on the way" and I spent miles on that assumption won't work?
You should still get them. Just a little patience....
Chase confirms what I've said for years regarding churning their cards:http://www.dansdeals.com/archives/12103/comment-page-2#comment-75199