Saw this just recently in an unlocked copy of CN AUNZ Sensis 2013.20 which I obtained somewhere (not here) that had no "F:" record. It also would not let me change the header name although the two things, missing "F:" record and the unchangeable name didn't occur to me as being related at the time. Figured someone had played around with it, and because i found it was also missing a map tile I therefore didn't use it. I dug the image out of the recycle bin when i came across the thread:
201320aunzsensis

Filled out the FID & PID under the Join tab in GMapTool 0.8.11 and voilą, now it has both "F:" and "P:" records:
201320aunzsensis
Header name can now be changed.

So sad, i'm just gonna bin it again. Oh well, it is only Sensis anyway.