One of the things I appreciate about the Superman films, actually, is that Lois Lane is in love with the man who is Clark Kent, in a certain sense; she just doesn’t know it (and yet, on some level, she does).
A non-believer could theoretically be exhibiting a great deal of love of God, without knowing it – through love of neighbor, for example. Their “state of grace” could exist on the level of an almost pre-conscious intuition.
Or, as been pointed out elsewhere on this forum, an atheist can profess no belief in God and yet have a quite strong belief in morality. If God really is love (as per the epistle of John) then this means that such a non-believer has not truly rejected God, in his heart.
If this atheist comes to some conscious awareness of divinity during his lifetime, all-the-better; but I don’t think that conscious acknowledgement of God is necessary to acceptance of God (and, ironically, there are many who consciously acknowledge God–with their minds–yet reject God–with their hearts–by using God as a means of indulging hatred or intolerance).