Not that this will ever be an issue, but what is the process of removing a moderator from office if he/she ever goes rogue or fails to meet the expectations of the community at large?
If you just have a minor concern, try contacting the moderator directly or starting a meta thread about what concerned you. You should be able to fix the problem with simple discussion.
If it's a very serious issue, you might be best to just explain this outright to the SO team. You'll find a "contact us" link at the bottom of every page. They can see what has happened and take appropriate action without there needing to be too much drama (the bane of all communities).
We recently published a process just for that: Handling Calls to Remove a Moderator.
It's intended to be a last-resort kind of approach, though. In most cases, simple mistakes and disputes can be easily resolved here on meta.