George is right, in fact unless the scenery has a PF designator (PF01 PF02 etc) then it will not show up in the GPS as it does not have the right type of bgl file to show that, they are just scenery, not "Airstrips"
That is the primary reason for the maps and the Triptix, to help you find them.
For any of the PF sceneries to show up in FSC or PlanG you need to rebuild the programs own database (or import it in the case of PlanG)
As a side note, if you check the PlanG database thread in this forum, Dieter has already provided a downloadable database for PlanG that will show all the non PF locations.