So you can't possibly know if he sold them all to a trusted few. Unless of course you are him the great satoshi. Just playing with us.
Satoshi's addresses have remained untouched, so the only way for such a trade to happen would be if he sold the actual private keys for the addresses and the buyer didn't move them immediately afterwards.
Since most of the coins are mined using various addresses that aren't affiliated with one another, there would be no way to prove that they belong to satoshi or others. There were no evidence that satoshi stopped mining right after 2009 and he could have mined throughout the years using other addresses. Satoshi has also made a transaction to hal finney so the addresses were not all untouched.