Simon Girty's brother George led the Indian attack against a detachment of American forces led by Colonel Archibald Lochry on their way to General George Rogers Clark's army. Every man in the detachment as either killed or captured; for months no one, including General Clark, knew the fate of those involved in "Lochry's Defeat." My ancestor, William Roark, was one of the lucky soldiers; he was captured, not killed (called William Noach (#47) in the list of 64 captured prisoners here).
Simon Girty, one of literature's villains, was mentioned in Major Richardson's War of 1812 book (see excerpt below). In Major Richardson's book, Simon was fictionalized as "Sampson Gattrie" in Major Richardson's book "The Canadian Brothers."
Was it the infamous George Girty, Simon's brother, who claimed land in St. Charles, Missouri? I would say yes.