Restarting the computer doesn't remove Normal.dotm but it is possible that something else caused it to be deleted or moved. It is also possible that your missing building blocks were never actually in Normal.dotm. By default they would go into a different template known as Building Blocks.dotx
Are you positive that the missing building blocks were in your Normal template?

Word will re-create Normal.dotm if it doesn't find it when it starts up.
What date is on the Normal.dotm that you can see? Does that date coincide with when you noticed the missing building blocks?
Have you also done a wider search for any copies of Normal.dotm on your computer?

Pedants Corner: Terminology matters -- Normal.dotm is a template and no template (or document for that matter) contains lots of templates. A template can contain building blocks which is the correct name for what it appears you call AutoTexts and/or templates.

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Andrew Lockton
Chrysalis Design, Melbourne Australia

Hi Mate, I appreciate your reply.
The recent normal.dotm file I was able to locate was from a day after the building blocks disappeared. The next earliest file was from 12 months ago and was missing quite a few building blocks that had been added. It's bizarre that they just one day weren't there.