This report from Matthew, I believe relates to our lives where although we know Jesus, but under life's stress' at times, we panic and forget about the word of Jesus.

Under severe conditions, the disciples like ourselves should have remembered that Jesus would always assist.   

Jesus would have known the future of these two and spoke accordingly.

The separation from God and family is clear but not clearly understood by me. I think Jesus may have indicated that the dead is dead but His concern was with only about the life hereafter