The Lee Smith you are looking for does not sound like the one buried in Mt. Idaho, but here is the info just in case. (Mt. Idaho is a long way from Riggins, about 55-60 miles).
Mt. Idaho cemetery records show Lee Smith B. 2 Apr. 1860 D. 29 Jun 1948. Has a dbl stone with Daisy Smith, his wife. Most of the Smith family lived in Mt. Idaho for many years. There is a Thomas Lee Smith buried there as well B. 30 Jan 1910 D. 3 Jun 1989. I remember Tom well, as I grew up above Mt. Idaho.
There is a new cemetery book out for Mt. Idaho that is for sale by the local Genealogical Society. http://idaho.idgenweb.org/Books/MtIdaho.htm
Also, "if" there was an obituary it would definitely be in the Idaho County Free Press from Grangeville, as that was/is the local paper. If you have a death date I would be happy to look through the microfilm for an obit.
Almost all of the cemetery records for Idaho County are on the Idaho County Genweb sitehttp://idaho.idgenweb.org
The listings for Mt. Idaho are not updated online yet, but I have all of the new info and can look up any burial you are looking for.
I have looked in all my cemetery listings and do not find another Lee or Freddie Smith. I thought perhaps he was buried in Riggins, but do not see him there either. Sounds like perhaps there was a small family cemetery.
If you find out there was, please let me know and I will be happy to help locate it for you.