I agree, George, that this seems to strain credulity. Especially for a man who never moved from the city of his birth. He certainly wasn't born under a wandering star. But the 1860 MS Census Index lists only 2 R. Bridges residing in the state: R.L. in Yalobusha, and R.M. in Yazoo. R.M. was 17, and residing with his mother and her husband, John Smith. In 1870, there are still only 2: R. remains in Yazoo; and another Richard in Panola.

Robert Bowman, in 1903, listed 14 companies that formed from Yazoo citizens. R.M. Bridges appears in at least 3 of them. I haven't checked the ones that went to North VA.
Co K, 10th MS Inf.
Co C, 46th MS Inf.
Co K, Wood's Confed. Cav.