There's no way for you to get the diamond without someone with developer access doing the following:
- Giving it to you through developer tools
- Manually executing a query that essentially does what the tool would
Whenever someone is promoted to moderator by appointment or election, an entry is made in a user history table indicating that your access changed, and the name of the developer that did it:

There is no such user history event for you on the main or meta site. I checked, just to make sure someone didn't accidentally click on the wrong profile while granting access.
In order for you to have a diamond, there must also be a corresponding history event. While I'm going to look, I can't think of any possible bug or scenario that would end up with a diamond / moderator status next to your name, without access to the tools, as seen from your profile screen shot. So that basically rules out either possible scenario:
- You weren't given access by someone that has access to the developer tools
- We don't have a rogue developer manually running queries to avoid logging of diamond grants
Unless there's some information that you didn't include in your report, I'm sticking this right behind Big Bird in my filing cabinet ;)