Whoo hoo! I found Edward Thorp's grave! It turns out that Edward was indeed buried near 'Marcus Lake' but that was a mispronunciation. It is actually 'Market Lake'. The town of 'Market Lake' has been renamed Roberts, Idaho. And 'Eagle Rock' has been renamed Idaho Falls, Idaho. Market Lake (Roberts, ID) is approximately 4 miles (not 40) north of Idaho Falls, Idaho. And Edward Thorp's grave is located in the nearby town of Teton, ID, in the Teton-Newdale Cemetery. There is a photo of the tombstone on Find A Grave.com.This was originally in Oneida County in 1886, but today it is part of Madison County, Idaho.
According to the photo of the tombstone, Edward Thorp died on December 21, 1886 and was aged 54 years, 2 months, and 18 days. That would put his birthdate at Oct. 3, 1832.
I also found a land patent with the BLM for the heir of Edward Thorp: Samuel F. Taylor (I don't know who he is). The accession/serial #is IDIDAA050520. The BLM serial #IDIDAA050520. It was issued on 5/4/1888 at the Idaho Land Office. It was for 240 acres. The Document Number is 51. The patent was for Township 6N, Range 40E, Section 11, S1/2SE and also for Township 6N, Range 40E, Section 14, NE part. These are both from the Boise Meridian in Madison County, Idaho.