Just send a note to customer service about your delay.

Say you already had boarding pass, and yet were bumped.
Be polite, and a goodwill gesture of some sorts will come your way for a 4 hour delay.

I assume you were bumped from the EMB120 to the B1900, in my 2 years of commuting on Gulfstream FLL/PBI-MHH, I only saw this happened when the loads were light, so it was probably a last resort for them