You could say the same of anyone who has ever died, for some sense of "valid" ... This, and similar waterfall-type arguments lead me to suspect that we haven't satisfactorily defined what it means for something to "happen."

It depends on the natural laws the person lived under. The next "valid" state of a dead person is decomposition. I don't find the waterfall argument compelling because the information necessary to specify the mappings is more complex than the computed function itself.