As Neil said above, that is the view we get from Scripture.I'm surprised by some of these answers. I thought the typical conservative view is that faith comes by hearing the Word, and that's how God saves His elect.
The original question was, "Can the Elect be saved without the explicit preaching of the Gospel?"
That is a distracting hypothetical with an easy answer from John the Baptist:
Mat 3:9 And think not to say within yourselves, We have Abraham to our father: for I say unto you, that God is able of these stones to raise up children unto Abraham.
The real question is, "Does God save without the explicit preaching of the Gospel?"
Apart from a few isolated hints like with infants in the womb, the answer is no.
Rom 10:17 So then faith comes by hearing, and hearing by the word of God.
It seems the premise of the question has to do with how do we defend God against charges of being unfair? That is not our job. Nevertheless, Scripture also provides clear guidance on that charge. The book of Job. Isaiah 45. Romans 9:15. Etc.