This is a hard to reproduce corner case, but it's not quite a bug. If you weren't aware, we recently introduced honeypots for anonymous suggested edits.
The spam notification is completely unaware of audits, and audits are completely unaware of the spam notifications (however, audits do know when something was rejected as spam, that's why it chose the edit as an audit). The actual notification that tells you that the message was identified as spam comes from something completely different.
What happened is, the post was rejected so recently that the origin was still being tracked by the spam filters, which is why you got that message. In effect, this should cause anyone to slow down and take a good look (audit or not) before suggesting action.
What's weird here is that you got the message after passing the audit, which wasn't very useful. However, as audits should represent the 'real deal' as much as possible, I don't see a reason to not show the extra notification when you happen on something in an audit that originated from something we're tracking as abusive.
Not marking bydesign because the order is backwards, but we probably should show folks that something is being watched by the filters during audits.