Our Lord in His teaching never once referred to unanswered prayer.  He said God always answers prayer.  If our prayers are in the name of Jesus, in accordance with His nature, the answers will not be in accordance with our nature, but with His.  We are apt to forget this, and to say without thinking that God does not always answer prayer.  He does, every time, and when we are in close communion with Him, we realize that we have not been misled.

Oswald Chambers

And whatever you ask in My name, that will I do, that the Father may be glorified in the Son.  John 14:13

If you abide with Me, and My words abide in you, you will ask what you desire, and it shall be done for you.  John 15:7

And whatever you ask in prayer, believing, you will receive.  Matthew 21:22

Now to Him who is able to do exceedingly abundantly above all that we ask or think, according to the power that works in us… Ephesians 3:20