Russ, a little more nudging, trying to circle back to your thoughts on who helped Waltz cover the mine. Moving on from the Walker/Weedin version of Weiser dying at Walker's Ranch...
Here's how I understand the history of the assignment of "Jacob Wiser" as a partner to Waltz: Ray and Elizabeth Howland, circa 1927 or earlier, but first appearing in Douglas's 1931 article; Jim Bark in the Bark Notes at some point prior to 1932 (He says the partner in the Weedin/Walker story's name had been forgotten, but Bark writes in his manuscript that he feels it must've been Wiser); Sims Ely in a letter to Northcutt Ely says essentially the same thing in 1932; John D. Mitchell in Lost Mines of the Great Southwest, 1933. And later authors all picked up the story. But these seem to be the first public mentions a partner with a name like "Wiser".
Some have speculated that the name "Jacob Wiser" came from Julia and/or Rhiney, which makes sense to me, but who knows. Many think that the concept of Waltz having a partner named Jacob came from a mixing up of the LDM and Lost German mine legends (Jacobs/Ludi, AKA Jacob and Paul Ludi). Mitchell, however seems adamant that his LDM story including Wiser had nothing to do with Jacobs/Ludi.
Back to the nephew. Matthew has put forth the possibility of Peter Backens, who was a real person that was a mining partner of Waltz's. He seems to have disappeared in the late 1860's. Some have thought that maybe Jacob Weiss was the nephew. He was definitely German, and also a mining partner of Waltz's who came to AZ from CA, but he died of fever in Prescott in 1867. One person that I've never seen mentioned as a possibility is Nicolas Weiss. He was Jacob Weiss's brother, and the two of them had a homestead in Osborn Valley (up by Mayer AZ) in the 1860's. If Jacob Weiss was Waltz's nephew, it stands to reason that Nicolas was as well. Nicolas seems to disappear after 1867, much the same way that Backens did. The homestead in Osborn Valley was taken over by other people and is still part of a working ranch today.
As far as I know, there is no public evidence supporting any of these men as Waltz's nephew, so I would put it in the category of "maybe, maybe not." And, who knows what Waltz meant by "nephew"...could've been any one of many family relations that fit the bill, or the son of a dear friend.
Brownie Holmes believed his Dad recovered the skull of the nephew, right where Waltz told him he left the body (Agua Escondido). There's corroborating evidence that an actual skull really existed, it was thought to be that of Waltz's nephew, and that Doc Jones had it, just like Brownie says.
So there you have it. If you think Waltz needed help to cover the site where you think the mine might be, well the argument can definitely be made...that even if Jacob Weiser was dead, either by Indians at the mine, at Walker's, by fever in Prescott, or by Waltz's own hand...there's plenty of evidence/speculation for the nephew being someone else.

Have fun on your next trip. Do try to bring out some rich gold ore next time
PS: I forgot to add, you brought up Bick's directions from his article as leading right to your canyon...he did mention a partner to Waltz also a German and also named Jacob in his article, and in all likelihood he heard that from Julia...no last name of Wiser, but still a pretty good pedigree if Bick's article is your roadmap, and definitely doesn't preclude a German nephew coming on the scene later.