The best implementations of "forgot password" seem to just send the email to the address in the login field without having to go to a separate page or have you re enter it.
By a similar idea, it stands to reason that if someone is putting an email address into a forgot password line that they believe they have an account. A really nice implementation would be to just start them on the path when they press the "send" button. If you just need an email, create the account and let them fix the password via email maybe.
You could also just go off in another direction and have the forgot password "error message" actually just putting them in the middle of a filled out create account page. "It seems like we don't have that account. Do you want to set it up?" might be a good message at the top.
All that could turn what can be a frustrating experience into somewhat of a nice one.