What Happened to My Unanswered Prayers?

Some time back, I sent an email to my friend’s Gmail account. However, for many weeks there was no response from my friend. Then I wrote another email to him to the other email ID of his that I had. He promptly replied. Later we discovered that the mail I sent was sitting in the Spam folder of his Gmail account. My mail was automatically filtered to the spam folder!
This made me contemplate on the prayers. I have been praying ever since my childhood. From short bed-time prayers to long intercessory prayers, pastoral prayers, prayers for the sick, in desperate need, etc. God answered some prayers but many are yet to be answered. What is happening to those prayers of mine that are not answered? God did not get it, or are they sitting in his spam folder?
I wish I could just visit heaven and see what is happening to those prayers of mine that are not ever attended to. For that, I will have to wait. However, God has specially favored John the Apostle with some special privileges. One such privilege is that he had an opportunity to peep into heaven and the throne room of God.
In Revelation chapter 8, John reports from heaven what is happening to our prayers. I draw a lot of encouragement from those words. In verse 4, we see that the angel who stands in the throne room of God offers the prayers of the saints to God along with incense. Verse 3 clarifies that the prayers are held in a golden censer. A similar picture is found in the fifth chapter also. Here the twenty-four elders are offering the prayers in golden censers before the Lamb who is our risen Savior. In this picture the incense are the prayers of the saints held in golden censers. They have harps in one hand (symbolizing praise) and censers in the other (symbolizing our prayers).
With this assurance, I still pray though all my prayers are not answered. I pray because I am assured that my prayers are not going to the trash bin, nor are they deleted my mistake. They are offered to God. They are valuable to God: the cries of anguish and questions that I presented in my prayers are so valuable to God so that they are offered in a golden bowl before him.