This retrieval failure is called Tip Of the Tongue or TOT.
Memories are classified as declarative memory and procedural memory. Declarative memory is static and procedural memory is dynamic in nature. Declarative memory describes what things are in the world for instance how to spell words, remembering birthdays etc.; procedural memory describes how to do things in the world for example ride a horse.
Flashbulb memories are those memories that are not erased and remains in the memory bank and they seem like as if they just happened. Some memories might change or distorted, but these memories remains in the memory bank. Flashbulb memories are those, which has significant importance in a person's life that cannot be easily forgotten.
People's shared experiences could be examined to study flashbulb memories. The examples of flashbulb memories were the assassination of John F. Kennedy, princess Diana's death, Challenger space shuttle disaster, Iraq war, recent terrorists attack, etc.
The writer has his share of flashbulb memories. Since childhood the writer has a great crush on one of the pop divas in his country. He almost fell in love with her at the first sight. Since she was popular it was very difficult to meet her. On her countrywide tour she came to the writer's city. At the time of the event the writer managed to skip into her rest room. At first she was astonished but when he explained about his crush she let him to stay with her the whole day.