I guess I'm wrong, but I read that they try to give it to people just starting out in their field, to encourage them to continue, rather than as a prize for finishing.
Update: user "ISL" says "that was Nobel's original intent, but the reality of the prize has changed with time."
Yes, Nobel Prize is only given by living people to encourage innovation rather than remembering the death, yes. However, it's very common for the Nobel Prize to aware scientists after a discovery has been made. Nobel Prize of Literature is the same, I believe.
For example, Albert Einstein won the Nobel Prize in 1921 for "for his services to theoretical physics, and especially for his discovery of the law of the photoelectric effect", but Einstein's relevant papers were published in 1905 on Annalen der Physik, it's 16 years later after the discovery. Another recent example is the Nobel Prize of Physics of 2014, given to Isamu Akasaki, Hiroshi Amano, and Shuji Nakamura for blue LEDs, it's also 20 years later.
Due to this very reason, The Breakthrough Prize was established in 2012 by multiple entrepreneurs, including Mark Zuckerberg, as a prize, which its proponents claim to be that they try to give it to people just starting out in their field, to encourage them to continue, rather than as a prize for finishing. Although it has received some criticisms of being a rockstar award as well.
Is it, by any chance, the prize you were thinking about?