I know he wasn't in the last season because Dan Blocker had died, and they killed Hoss. But did they ever say how Hoss died?

I don't remember anyone on the show even mentioning that Hoss died.

http://mentalfloss.com/article/28798/first-time-tv-show-addressed-death-character

I don't remember anyone on the show even mentioning that Hoss died.
in one of the lost episodes Ben mentions in one scene that he was killed while rescuing someone or something. And I read that there's a 2 part lost episode where they show it happen.

Thanks for the link, Mr. Television.

From the article:

"The Lack of Hoss

While "Forever" never directly dealt with the actual circumstances of Hoss' (or Blocker's) death, many scenes were obvious references. Said Landon about the episode: "We try to mention Hoss' death very simply, in passing... it might not please everybody. I'm sure that some people would rather have a whole hour memorial to Dan, but we just couldn't do that." He added, "We tried to do what we thought he would have wanted us to do.""

I guess it was mentioned a bit too simply, in passing. I'm pretty sure that when I saw this episode (in reruns) I didn't actually know Dan Blocker was dead.

Also from the article:

"But by far the most emotional scene is when Ben and Joe visit the burnt remains of the cabin where Joe's wife and unborn son were killed. In the scene, Landon collapses into Greene's arms and the two are seen shaking and crying. It was plainly obvious to the entire cast and crew that these were not fake or "crocodile" tears; the two stars were weeping for real, for their beloved friend and co-star. (After the director yelled "Cut!", many of the cast and crew joined the two stars in their open grief and wept.)"

This sounds weird to me. Filming your sorrow about a beloved friend's death while acting a scene crying over the loss of a character.

"Throughout that final season of the show, Ben Cartwright speaks of the loss of his beloved son Hoss, though exactly how Hoss died is never explained. It wasn't revealed until years later, in the syndicated follow-up series Bonanza: The Next Generation (1988), that Hoss drowned trying to save another man's life."

As much as I liked Hoss and think Dan Blocker was awesome, Bonanza was on it's last legs with or without Dan Blocker. I don't believe that Dan being in season 14 of the show would have saved it from cancellation.

I haven't seen the 1st episode of the 14th season since it first shown. At the time didn't watch the show that much and didn't know Parnell Roberts had played older brother Adam. I wonder if Parnell was asked back for episode or two. It would have been nice to say have Adam come with his wife and child and spend a little time with brother Joe and his Pa.