Several more possible information sources, thanks to pegleglooker. When I started work on my cross-reference index in the 1970's, I didn't consider the possibility of poor spellings. But they exist and can affect everyone's ability to research.
Under Earl Dorr's lost placer gold, I have references for The Complete Guide to Treasure Hunting on pages 215 and 224; an article which appeared in True Treasure for Winter of 1967, p. 20; and Penfield's Treasure Guide to California, page 77.
I also have a reference to "RI, 4", but I don't have all my sources entered yet, and don't know what this is. Definately Earl Dorr (Dour, Door) is the central character, and located in California.
There is also a Cave with an Iron Door, but that's in Oklahoma.