There are quite a few "lefties forced righty": Joe Perry, Mark Knopfler, Gary Moore, Billy Corgan, Duane Allman, Gregg Allman, Noel Gallagher.
Hendrix was of course a lefty, but learned guitar righty, then switched to lefty for stage, yet interestingly retained righty for composing even after he long only played lefty on stage.
The only "righty who stumbled into lefty" I can think of is the late Ed Gagliardi of Foreigner (first two albums and later on with The Spys), who as a righty played a lefty Ric 4001 in lefty position because he had accidentally learned bass on a derelict lefty bass. Mick Jones fired him for being "too busy" on bass and got Rick Wills instead.