They found glass in his teeth indicating cyanide. There were people who claimed he died and where since the 40’s. Unlikely his lived and was brought back.
He was eventually found 35 feet from where they said he would be found.
All that is true, the area where Borman’s body was found was years after they had searched that same area multiple times.
Like I said, the most likely scenario is how you describe it, with a very, very small chance he made out to Argentina.