The following is a good reminder from E.M. Bounds that "ask and it will be given to you."
Two cases of unanswered prayer are recorded in the Scriptures in addition to the Gethsemane prayer of our Lord. The first was that of David for the life of his baby child, but for good reasons to Almighty God the request was not granted. The second was that of Paul for the removal of the thorn in the flesh, which was denied. But we are constrained to believe these must have been notable as exceptions to God's rule, as illustrated in the history of prophet, priest, apostle and saint, as recorded in the divine Word.
The Possibilities of Prayer, 105.