Unfortunately, he had met with no one on the way there or back who could vouch for the truth of his story, but luckily he had kept the note, and it would be produced as evidence. 
He didn't see anyone on his way home but he still held the letter which was ample evidence.
mnli hypothesis: He didn't see anyone on his way home but he still held the letter which was ample evidence. premise: Unfortunately, he had met with no one on the way there or back who could vouch for the truth of his story, but luckily he had kept the note, and it would be produced as evidence. 