Well burning, you obviously had a hunk of poo(get it burning,,, poo) wedged in there that it now gone... are very rare occurence. unless you run in alot of mud. the mud prolly help the poo in but let go right after you stopped or went into reverse, the point is, it did the damage and now gone. Your front drive shaft is not ruined, it will function, but....

good clean-up btw