hope not to late, i am a contractor working on a project for a company not registered in USA. recently when arriving to USA to visit this companies' local offi

hope not to late, i am a contractor working on a project for a company not registered in USA. recently when arriving to USA to visit this companies' local office i was stopped at border control and almost denied. took 8 hours and a body search to get out of there. how to explain clearly to immigration officer this situation.