Glad you are OK and everything else is repairable!
Like RoyF, I'm not understanding why your description of releasing the hitch from the pin. When we had a 5'er, I always extended the jacks until the weight was just off the hitch plate and then I would pull the release arm.
Well, I say always but there was my "I did it" time, too. We had not had 5'er long and just returned from lake where I was pulling 5'er and wife pulled boat with our Durango. Some numbskull almost caused an accident by pulling into the Durango. When we got home she was still pretty upset. I guess that kept me from thinking clearly so when I was unhitching 5'er, I just pulled release arm to at beginning of process...no jacks down, trailer wire still connected, tailgate up, no wheel chocks, nothing! The 5'er immediately proceeded to roll back and somehow luckily the hitch box caught on the still raised tailgate and bent the living heck out of it but the only damage to truck bed was a tiny dent on top of one side. I was totally uninjured but almost sick. I folded my arm across the top of the truck bed sides and just laid my head down. My then 13 yr old daughter runs into the house and tells wife what happened. She runs out and see me leaning on the truck bed and thought my arms were chopped off or something. Later, the wife said it was the first time she had heard daughter say the F word...evidently her report was "Daddy broke the f...... truck!"
Anytime I see somebody here say they will never have an accident because they do so-and-so, I just think never is a long time!