We cannot ask Alf Doten himself, but we can check his diaries:
 
In the 1960s, into the 1970s, author Walter Van Tilberg Clark heavily  
edited the diaries of Alf Doten into three volumes with a total of 2,224  pages, 
plus appendices and index, published by the University of Nevada  Press. To 
the great frustration of historians in Nevada, the published  pages 
represent perhaps a half of Doten's extensive files. From the entries  about Twain, 
below, I think it is doubtful that Doten was the  jokester creating the bar 
tab story. I also doubt that editor  Clark omitted any mentions Doten made 
of Twain. After reading all the  Twain entries in the Index, I append those 
I think you will agree make  it highly unlikely that Doten gave enough time 
and attention to Twain  to bother with creating the bar tab story.
 
On Page 767 (Vol. 1), Doten wrote:
Sunday, March 6, 1864. Clear & peasant. rose late. AM I went to  Creoss's 
awhile. J.D. Winters introduced me to "Mark Twain" --had pleasant  little 
chat with him.... [no further mention that day of Twain.]
 
Then on March 4, Doten, who is living in the mining camp of Como, some  
distance from Virginia City, writes: ...Evening stage brought a noted  
correspondent of the Territorial Enterprise who writes under the"nomme de plume"  of 
"Mark Twain."  His name is Samuel Clements.  [sic]
 
The next mention is on page 830, (Vol 2) 1865: Sunday, April 9. ...Went to  
Sutterleys -- took my portrait twice--small cards, and one big picture to 
hang  up in the gallery with Mark Twain and Dan DeQuille. [Sutterley's is a 
photo  emporium.]
 
Page 900 1866: "Mark Twain" (Sam Clemens) arrived this evening from  
California. D. E. McCarthy, one of the former proprietors of the Enterprise came  
with him.
 
There are other, later, mentions of Twain, but none pertinent to this  
discussion.
 
Bob Stewart
Carson City