There are several reasons why the Beale Story can not be true but there is not one good reason with documented proof to prove that the story actually happened...
... This makes the work nothing but "FICTION"
There are hundreds of other reasons. Such as the iron box missing, TJB's letters missing, C1, C2 and C3 code papers missing, the author's name missing, a copy of the Job Print Pamphlet at the Library of Congress missing, no newspaper listing any of the party traveling to and from Sante Fe, no newspaper article of the 30 party associates missing or presumed dead. The list goes on and on and on. No records in the Spanish Archives of the party of 30 coming into Sante Fe, staying in Sante Fe, leaving Sante Fe or returning purchasing mining supplies. The story was for profit not for a real treasure.
Franklin, this is what many fail or refuse to realize.
They always go to the could have maybe references of unidentified parties, lost mines, tales of Indian massacres, anything that can keep up the hope that the Beale treasure is real, but NOTHING that can be directly connected to the "perilous adventure" narrative in the Beale Papers is ever brought forth.
Its always "no proof that it happened or no proof that it didn't happen" while missing the very basic point of NO PROOF.
On another thread, those involved with the creation, copyrighting, printing, publishing, advertising, and sale have been discussed in detail, and yes the original motive appears to have been a dime novel with play along ciphers for profit.
50 cents was a hefty price in 1885, but copies were withdrawn from sale due to three families objection to their ancestors names being used in the job pamphlet.
A second edition could have been printed with those family names removed if this was a true treasure story and the unknown author wanted to get the word out for his own known reason, but, alas, that never happened, and the whole episode would have been forgotten if not for N H Hazelwood getting the Hart's involved with sheets of ciphers.