Normal Style Disappeared From Style Pane

If normal is always hidden, it will not show up in the styles pane.  To fix this, go to Styles pane > Manage Styles button > Recommend tab.  Select Normal from the list and click the Show button.

Frankly, I know little about restricting formatting because I don't use it.  But I'm trying to duplicate your result--and can't.  When I go to the restrict tab and click select all > restrict, everything get restricted except:

Default Paragraph Font

No List

Normal

Table normal

And when I select Normal or any of the other three, the Restrict button is greyed (unavailable). This is what I expected because these four items are among the mandatory styles in Word that cannot be deleted from a document (the others are headings 1 to 9). 

Try creating a another based on your template.  Does it have only the expected restrictions?  If yes, copy everything but the last paragraph mark (if the document has section, do this section by section) into a new document based on your template. Is Normal still locked?  Are the other style restrictions as you set in the template?

It looks like I may have been mistaken: in the "broken" document based on the "working" template, somehow the style "Normal" was changed in Manage Styles to "Locked" (Styles pane > Manage Styles Restrict).

Normal still shows up in the Styles pane in the dotx template (even though it is marked Hide Until Usedon the Restrict tab); yet, in the "broken" document based on the template, Normal is shown with a lock symbol in the list under the Restrict tab?

I'm the only person with the password, so it almost looks like some set of user keystrokes might be changing Normal to restricted. Is that even possible?

Here is one test I tried to see if I could get Normal to be hidden by copy/paste activity:

• Created a new document (.doc) based on the document template (.dotx).
• Confirmed that Normal was visible in the Styles pane of the new document.
• Created a second new document (.doc) based on the document template (.dotx).
• Copied all the content from the first test document (all except the last blank line with a Paragraph symbol).
• Pasted all the text from the first document into the second document.
• Confirmed that the Normal style is still visible in the Styles pane.

Here is another test:

• Created a new document (.doc) based on the document template (.dotx).
• Confirmed that Normal was visible in the Styles pane of the new document.
• Opened the "broken" document that has the locked (Restricted) Normal style.
• Copied all the content from it down to the final paragraph symbol.
• Pasted the "broken" content into my new document.
• Confirmed that the new document still displays the "Normal" style.

I should mention that the way I know that the "broken" document is based on the template is that it has the same version as the template listed in the Comments field under file properties.