At one time the subdomain was always username.bravehost.com but now they let you use a different name. If you opened the account specifically to start a web site then there is a good chance that you used the same name for both.
If you have any other services registered then you can get your user number from them and raise a support ticket.
I keep a special email folder with all the sign up messages for things that I register. Makes life a lot easier when I can't remember userids or passwords.
if you don't know your bravenet login information do a lost password and see if it sends your password and such to your e-mail address of record with your bravenet account
make sure to check junk mail/spam folders as well
if you don't receive an e-mail then it got list in cyberspace and you will have to open a ticket
hotmail, gmail, aol, msn, yahoo are e-mail addresses that have strict filters that will only allow so much through and all