I could be wrong as I am speculating from very limited information but it sounds like these are fields from a related table occurrence. They may be inside a portal or they may not be. In layout mode, they'll show :: before each field name if I am right.
If that's what's happening here, FileMaker is allowing you to enter data into the related record, but either nothing is being entered to form a valid relationship between your layout's current record and the related record or the data doesn't meet the requirements of a portal filter if you are using FileMaker 11 and these fields are inside a portal. Either way, once you commit the records either the relationship or the portal kicks in and hides this data from your view. If you open a layout directly to this record, you'll find the data is present in that table, just not visible on your tab panel #3.
You'll need to check relationship settings and any portal filter to see figure out why this is happening.