We need not be discouraged by the problem of supposedly unanswered prayer. I say, “supposedly” because I challenge the supposition. While God has not bound himself to hear unbeliever’s prayers, his promises to answer the prayers of his own children are categorical and inclusive. It must then be wrong to think that a flat no is ever the whole of his response to reverent petitions from Christians who seek his glory and others’ welfare. The truth must be this: God always acts positively when a believer lays a situation of need before him, but he does not always act in the way or a the speed asked for. In meeting the need, he does what he knows to be best when he knows it is best to do it.
Knowing Christianity, J.I. Packer, p. 104