i dont know if your dist company is wanting licensing for a particular sample, but if you purchased STP and have registered it, and you composed the music, its yours. if you have a copyright for the music then that is all the dist company will need to see. if i was you i would get an laywer you know to draft you some contracts for your clients and to copyright your music so next time you run into this situation everything will be ready to go with no problems.
hope this helps
Dan