Are both cams the same? By that I mean both have keyways, lobes in same position? If so, then for some reason you got 2 cams!!
How can you see where the keyway was? Has it been 'welded' & re-machined, if so, it can be ( very carefully ) centre-popped & drilled to take a small pin, & as said previously, no real load & more than enough to locate the cam.
Or, could it simply be a sheared key that's still in the slot & been 'smoothed' flush?
Either way, I'd have a go at drilling & re-pinning. An easy job, even in situ.