Missing Form Data

I recently created an Acrobat form and emailed it to someone to fill out for me. Because I knew the person was busy, I filled in a few of the field for her myself (i.e. name, phone and the like). I gave her instructions on how to use the form, (download to her pc, open file, fill in the fields, resave and email back to me with file attached).
 
When I got the form back it was completely empty, all of the fields, including the ones I had filled in for her, were empty. The integrity of the entire form itself was still there, nothing else was missing or corrupted.
 
I am guessing the user got confused or was inexperienced but even so, I am at a loss as to what the user could have done to result in a form with NO fields filled in (including the ones I filled in for her). I don't know what Adobe products the user had, but I am guessing she had only Reader.
 
I have tried recreating her result but have been unable to.
 
I am somewhat new with Acrobat and I really want to understand how this might have happened. I have tried asking the user, but she is busy and hasn't responded so far. Here are some of my questions -

1) Is there some setting or feature I could have turned on in the form to prevent this?
2) Could I have prevented it even if the user had Acrobat and not just Reader?
3) Did I leave something out of my form that would have either contributed to or directly brought about this result?
4) Are there security features that might have contributed to this or prevented it?
  
Your help would be appreciated. If you respond, please be precise.
 
Specs
Windows 7 Pro, 64-bit
Acrobat Pro Extended 9.4.5