I think you have to go back systematically.Gold Rush?I thought that was about the time of the Indian Removal just a few years before Thompson was born. I know 1850 censi showed people in Lumpkin county (where gold fields centered? working as miners, but were they mining gold).
Now, as to the Lemuel and Barbary Edwards Allen crowd.Do you have them in 1840 Habersham?Does your book show their census data then?Couldn't have stayed there long.I show a George W. Allen marrying Malissa Woods in Habersham in August 1839, but I have a G.W. Allen marrying Rebecca Stroud in Union in July 1842 and he is the one found by Barbary Allen in 1850 and 1855 Union.Plus, Lemuel Allen (like Robt. Allen) is shown in 1834 Union census and I'm thinking that was the Lemuel Allen married to Barbary Edwards Allen. If so, this family looks to have been in Union for about 30 years exepting a possible brief drop down into Habersham.