I am sorry, which word should I have used?
"Pre-mined" is a term of art signifying that coins were generated before the general public could participate. Pre-mining is generally regarded as a scam, and pre-mined coins as scam coins. To use that word with regard to Saint Nakamoto is gross sacrelege. Rather say "previously mined" or better yet "mined by early adopters" (because being an early adopter implies that any privileges were merited by your foresight, or because you were one of the Chosen).
The likelihood is that private keys of that vintage are no longer extant. Most of those coins have never been touched. They are still in their original reward.