The good Samaritan:
Luke 10:29-37
Jesus told the story of the good Samaritan in answer to the lawyer's question of who his neighbour was, after Jesus told him to love his neighbour as himself. The story explains the neighbour and doing good to the neighbour. And Jesus explained how doing good to EVERYONE, muslims, included, is what we should be doing. He never implied our neighbours are not lost. ANd He clearly taught we could only have eternal life if we believe on HIm and His name for salvation through the work of the cross.
The interesting this is that in many cases Jesus urged people to try to save themselves by good works, knowing no one could be THAT good. That was the case with the rich young ruler as well. He told the man to sell all he had and give to the poor to be perfect. When asked how anyone could be saved, after making the directive, Jesus said with man this is impossible. But with God all things are possible.
Anyway, the good Samaritan shows us how we should be good to all whom we meet and know. ANd saying people are lost in no way violates that directive.