Yes, I'd make the Lost Password form unavailable to logged in users, unless you can think of a reason they might need it. For accounts without passwords (Accounts created via Facebook connect, for example), there should be a separate 'create password' button on the Facebook Integration settings page.
No, I can't think of any reason why someone logged in would need it.
Equally however, I can't see how someone logged in would easily find that page unless they were determined to do so by logging out and then deliberately entering incorrect details, so I'm not sure it's an issue really.
Personally I'd keep it and add some extra functionality to it. If you use it when you are logged in there's two reasons:
You're using an automated login and forget your password (or you logged in and forgot it - small chance)
You're trying to annoy other users.
In the event of the latter, if they are doing this whilst logged in and you send the username/userid in the e-mail, the recipient knows that it is an idiot and can report them to the appropriate member of staff.