Inspect your .lgb file. It's plain text. Open it with a text editor. Notepad is fine.
It will have a list of files names without extension, each name usually ending on _georef.
An example for an .lgb file content:
Code:
tileMap-001_georef
tileMap-002_georef
TransDEM expects the actual raster maps in the same folder in which your .lgb files resides. And for each item in the .lgb file there are two files associated with it. They both have the same name, but different extensions, .trf and .png. The .png file is the raster image, the .trf file has the TransDEM-specific geo referencing information for it.
So, for my example, in the folder of your .lgb file you should find:
tileMap-001_georef.png
tileMap-001_georef.trf
tileMap-002_georef.png
tileMap-002_georef.trf
Is that the case?