How sure are you that it was the cadaver incident that stopped his tracking? just because he had a cadaver "incident" it doesn't mean he will be better suited to that line of work. Unless you have a very experienced cadaver trainer that has seen a natural dog then stick with tracking.
As with all dog training when you get a blip, take him back a couple of stages and get him enjoying the tracking again, I don't know how you end your track but why not end with a bit of meat, 49p hot dog sausages are a dream to teach a dog how to track, but no ketchup