Suppose he deposited it into AlphaBay and then withdrew from AlphaBay, and FBI didn't seize AlphaBay's logs. Where is the criminal immutable durable record now?

Suppose he deposited it into AlphaBay and then withdrew from AlphaBay, and FBI didn't seize AlphaBay's logs. Where is the criminal immutable durable record now? There is no proof of connection between incoming and outgoing coins. Same principle with mixers.