Weird indeed! I'm dying to know if there was an "enable" or "edit" button available on the screen when you first saw them lined out ... it almost sounds as though they were disabled, and then later deleted.
Hopefully, this is not the case, or it is some "glitch" that DH can readily/easily fix. I'm also hoping that some employee using mail on the account did not run afoul of TOS and result in a mail suspension.
I'm wondering if you have another primary email listed besides one of these addresses for DH to contact you in the event of an issue. There have been times when some enforcement/preventative measure has been taken, or some other condition exists, where DH would notify you, via email, of the circumstances but you would not receive that email as the email account they use to notify you is involved in the issue at hand.
One way to make sure that you have not "missed" any vital communication from DH regarding your account because you could/did not receive the email notification (email failure/etc), is to log into the control panel, and go to the Support -> Support History Screen.
Here you will find an "archive" record of all communication between you and DreamHost, including any emails that you, for one reason or another, never received. I would check that first to see if it sheds any light on the issue and, if not (or if they notified you of a problem), I would then Contact Support immediately so they can start to investigate what happened and get it resolved.
Good Luck, and I'd be curious to know what you learn.