I had a similar situation being rear ended with my cargo trailer attached. No obvious damage to the truck or reciever or stinger, some damage to the ramp door which the other insurance company paid for. I also said, new hitch, they complained, said no damage visible. I said, let your lawyers provide a document saying you will take responsibility for any hitch failure in the future or have the exisiting hitch taken off, magnifluxed and reinstalled. End result, new reciever and stinger and money to have a trailer shop examine all the mounting points.
Don't back down, IMHO it's not worth the risk.
Had I had my airsafe hitch installed I would have insisted on a new hitch along with reciever and WD bars. That would have been some serious coin on their part