Kerri, I imagine you are referring to George Gumbert, first son of William and Margaret Peck Gumbert. I do not believe this George is the one referred to in the book.
However, most researchers have not picked up on another George Gumbert, son of Christian Gumbert, Sr. Christian had at least three sons, Christian Jr. (b. 1784), George (c. 1794) and William (b.1798). These were, I believe, the three male children in the Westmoreland County 1800 census.
George appears on the Allegheny Township, Westmoreland County tax list for the first time in 1826. His name is deleted in the 1827 roll. Christian Sr, Christian Jr and William Gumbert are all on the same tax lists until at least 1830 (the last year I have records).
I have found no further information on this George. Wonder whether he left for parts West. Was hoping someone would have further info. Sandy