"Retroactive Prayer" was introduced to me by a "biker" friend in a Baptist church I attended long ago. It is prayer that we should have said and had forgotten to do so. I do this sometimes when I forget to say 'grace' when eating alone. Half way through the meal I realize I didn't pray beforehand (Giving thanks in all things, 1Th 5:18 and others). I then ask forgiveness and pray (one could say "Lord, bless all that is within me." 
Sometimes we hear of a prayer request and say we will pray for them, forget, then later wonder if it is TOO LATE to pray. If it is too late to pray, then there is no point in praying. But if we don't know it is too late, or if things are no irrevocable, Isaiah 65:24 comes to mind as an application, not as a promise. If God can answer before we pray and while we are yet speaking, then in His omniscience and foreknowledge God could know we would forget to pray, then remember and pray, and God could credit that to us and answer the prayer even before we pray it. I wouldn't count on this type of prayer, and would not purposely plan to utilize it out of laziness, but you might consider it at times.
Sometimes we hear of a prayer request and say we will pray for them, forget, then later wonder if it is TOO LATE to pray. If it is too late to pray, then there is no point in praying. But if we don't know it is too late, or if things are no irrevocable, Isaiah 65:24 comes to mind as an application, not as a promise. If God can answer before we pray and while we are yet speaking, then in His omniscience and foreknowledge God could know we would forget to pray, then remember and pray, and God could credit that to us and answer the prayer even before we pray it. I wouldn't count on this type of prayer, and would not purposely plan to utilize it out of laziness, but you might consider it at times.
