heightfield scripts and mission files

I have made my own heighfield script...which was basically a flat map made from a PNG. I loaded a PNG and applied it...and then saved every single file, the terrain file..the mission file, the heightfield script file, etc. But when I load the mission again the heightfield is not saved, that is, it loads the PNG file but it did not apply it, thus, the whole map contains hills which is wrong because my PNG suppose to generate a flat map.

Any help?

thanx for your time.