OK OK! This has got a bit out of hand here!
First off, I'm a member of the Vandalism Control Network, I'm a long-term recent changes patroller and new pages patroller. I'm a member of the counter-vandalism unit and so on. I hope you count this as "peer review".
Right, when you add [[Category:Missouri]] to a page, the page you added it to is automatically listed at the corresponding category list. So when you add [[Category:Missouri]] to a page, it is also listed at Category:Missouri.
In this edit LindaWarheads removed the categories from your sandbox page so your sandbox wouldn't be listed on the category lists. LindaWarheads gave an edit summary of "(Please remove +cats or article shows up)".
If your editing an article in your sandbox and you want to add categories to it, your best off using [[:Category:Missouri]] instead of [[Category:Missouri]]. This way the sandbox wont be added to the corresponding category list. Then, when you've finished the article and you're ready to create the article proper, simply remove the ":" from the category tags and create your article. 
ArmedCitizen, with regard to your comments above:
LindaWarheads did not make indiscriminate changes without justification. As LindaWarheads provided an edit summary, this is justification enough.
In my opinion, LindaWarheads did not act as a vandal and hide evidence of her actions.
I hope this ends the matter. If you don't feel it does please see WP:DR.
Also, please remember to be civil and assume good faith.