How do you know you haven't had spontaneous activation more often? If you know it it isn't spontaneous. You don't start explaining stuff and say hey this is all spontaneous activation. What happens is you own the information and tell it as the owner as if you've already known this a long time.
If you had a purpose for PhotoReading the book your mind processed the information. If you have a different purpose later. You do it naturally in many areas of life already. If you buy oil for your car. Put it in the garage with the intention to service your car later. And then someone steals your car and you get a new one. The oil is still in the garage. Say your brother comes to visit and says. I got to go I promised to service the wife's car. You say, hang about. I bought some oil for my car but haven't used it. You may as well take it.
Information in your head whether it's about oil you stored in the garage or words in the book is available to you. Purpose may change. If you had a purpose to begin with you're more likely to be able to remember where you stored it.
Your post did not invite discussion. You told everyone to wait for more so they waited.
Alex