Is it a mayabinary file or a mayaAscii file? if there's an error in the script editor with a line number you can save your file as maya Ascii and go and edit that line to be correct. Also try exporting the whole file to OBJ and reimporting the OBJ. This might also fix it.
Any errors in the script editor? It may be salvageable still, moreso if you have a recent backup. quick edit: What usually happens is some kind of bad data (ive noticed it a lot in UVs in particular), so maya just ends up discarding the whole model as a result.