A memory from a real event that was encoded, stored, but not retrieved for a long period of time until some later event brings it suddenly to consciousness is known as a

my good sir, your answer here is "jvhrwekjhvbebebjb"

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the answer is solomon northrup. he was a free-born african american, abolitionist and professional violinist that was drugged, kidnapped and sold as slave in 1841 and remained in captivity until 1853 where he regained his freedom with the of the then-governor of new york, washington hunt. he wrote and published his memoirs "twelve years a slave" in 1853, and in this text, he tells the story of his escape thru one of louisiana's swamps (the great pacoudrie swamp) in which he ended up covered in green slime from crossing the surface of the dead water.