When I list campaigns from the "emailmarketing/campaigns" endpoint, it shows one campaign with a SCHEDULED status that has actually been deleted, and shows correctly as deleted in the webapp. Any ideas?
After a quick look at this, it appears that you ended up with a campaign that was deleted while it was still in a scheduled state. This did prevent the email from being sent, but appears to not have fully updated the status of the campaign. In this case, the best work-around is to jump into the UI and temporarily restore the campaign in order to move it from Scheduled status to draft status. Once you've done that, you can again move it to deleted in the UI.
In this case, the API was simply reporting what it was in the database, which was a result of this status not being set correctly.
Regarding the campaign being stuck in a scheduled state even after being deleted, I will be looking into that a bit further so that we can take steps to ensure that it does not happen again.
If you have any questions, please let me know!