Assuming you mean "someone who believes god does not exist...", I would think the person (today) would conclude they dont know the cause of his recovery. There are many things that were inexplainable hundreds of years ago and were attributed to supernatural phenomena, but can be explained today. There is no reason to believe that sometime in the future there wont be an explanation. But just because something is inexplainable doesnt mean someone should assume god had something to do with it.
Suppose you had cancer one day and
the next day was cured. If your explanation is that god cured
you, then you would be laughed to scorn by the medical community. But now if they found some protein in your blood stream and that was the cure, does this make the miracle any less?

Then god also causes tornadoes, earthquakes, flood, etc that kill millions of innocent people every year... there goes the idea that god is benevolent.
But by admiting this world is not perfect then there must
be some way to leave it.