if you read a copyrighted material without paying and then forgot most of it a month later with vague recollection of what you've read the fact is you still accessed and used the copyrighted material without paying.
Now let's go a step further, you write something that is inspired by that copyrighted material and what you wrote become successful to some degree with eyes on it, but you refuse to admit that's where you got the idea from because you only have a vague recollection. The fact is you got the idea from the copyrighted material.