lamp out display problem

[NScott]

I recently had an an aluminum t g mountaineer bed (T & G Mfg & Sales - Home) installed on my 05 3500 Std. Cab 4X4. The truck was built with a pickup box on it from the factory, but I wanted an aluminum bed that was lighter because I only use the truck to tow heavy gooseneck type trailers.
Anyway, after the install the shop that installed it told me that my "lamp out" light in the dash display would remain on. He said he had installed several flatbeds on Dually conversions and that they had all shown "lamp out" on their displays also and that he had never figured out a way to turn off the light. Has anybody else had this problem or heard of it? How do you get the display to go out? Any help and experience in this matter will be appreciated, as this is not a critical issue but it is annoying to have the light on.