Wikipedia, "Colonel (United States)" suggests this military rank, "became rare" in the period after the Civil War; also "many brevet colonels were appointed again during the Spanish American War, prominent among them Theodore Roosevelt and David Grant Colson."

Although I suspect news about the time of his engagement and marriage would be a more timely reference, information follows that might help you locate an obituary. Have also included a news item that refers to him as "Colonel Charles Jay Foster."  

**On the trail of the obituary**:

With a 1929 death, there is at least a good chance the cemetery or mortuary has a copy of his obituary, or at least a newspaper reference. 

Do you have a copy of his death certificate? The (early) California Death Index reports his state [death record] file number is 28738. See entry, [Charles J. Foster (d. 9 May 1929)][1]; "California, Death Index, 1905-1939"; digital images, FamilySearch (accessed 2012), cites California State Registrar, California, Death Index; Office of the State Register; Sacramento, and the Butte County Courthouse, Oroville. 

[FindaGrave has memorial][2] for him at Cypress Lawn Memorial Park, Coloma, San Mateo County, California, 

Ancestry's collection of "San Francisco Area Funeral Home Records, 1895-1985," entry for "Charles Jay Foster" (dec'd 9 May 1929), reports the mortuary as N. Gray and Company; reports his occupation as "Retired Jeweler."  More about this mortuary and records on www.sfgenealogy.com; http://www.sfgenealogy.com/sf/sfranlib.htm#researchity. (Seemed to me perhaps better luck with the cemetery.) 

From the same funeral home, record for his widow, Mina (Bauer) Foster (d. 24 Oct 1943). Her parents John A. Bauer; Louise Hagen. (This seems the Bauer family with 9 yr old "Minna" at Austin, Texas in 1880.)    

**News item referring to family members; calls him Colonel Charles Jay Foster.**

Here is one of the news items; a dramatic story of the shooting death of a young woman. Charles Jay Foster is called "Colonel Foster." The woman killed is, it seems, his wife's niece. Oakland Tribune, January 14, 1913. 
![enter image description here][3]


  [1]: https://familysearch.org/pal:/MM9.3.1/TH-1961-26181-12441-58?cc=1932433&wc=14216746
  [2]: http://www.findagrave.com/cgi-bin/fg.cgi?page=gr&GRid=63689763
  [3]: https://i.sstatic.net/ln568.jpg