If SBF takes some form of plea deal (which he almost certainly will- Madoff did, and Madoff was smarter than this guy by an order of magnitude), it's basically guaranteed that a condition of his deal will be to disclose where all the money went- he won't be allowed to retain any of it.

That makes tracking down the little amounts worthwhile, because it only takes a tiny amount of money to render his plea deal null if it can be shown that he has broken the terms of the agreement.