This has occurred 3 times.  Steps to reproduce:

1. Navigate to my local version on my HD to upload it to a Web page form submission
2. Do the same the next day, only file has disappeared from both local and the Skydrive folder
3. Find it in the Recycle Bin, then do a Restore

The only thing different about this Word document is that 'Read Only Recommended' is checked. I have since unchecked it and saved it and will see if that is the problem.