I have just struggled with a problem and have narrowed it down a bit, I think. I am fairly new to xataface.
The problem was that some, or all the data was disappearing from the view form (even though it was there in the edit mode form) when I was trying to set up field groups. By trial and error, I have established that it only occurs when I place the very first field from a table, into a field group in the fields.ini file. My workaround is to add a field to the top of the table that I just ignore. Not perfect, as I still have a blank default 'details' group at the top in the view form, but otherwise it works.
The problem is repeatable. If I now try and add the new dummy field into a group, the same problem recurs. So it's not related to the actual field, name, or it's data. I also experienced the same problem on two different computers (both with the same Xataface files, but different versions of Ubuntu and probably Apache too)