Have you toggled the headlight button on the DCS remote? or tried a feature reset?
some models have the headlight picking up power thru springs. If the body shell was removed, these springs can loose power.
You could test by using 2 AA or AAA batteries (less than 3 volt DC) to see if the light still works by putting power to those springs going to the headlight.
I don't have the GP38-2 to look at. I will look up the instructions now.