Comment by olalonde
What I described is actually extremely mundane. Maybe you started with Bitcoin Core and later switched to a lighter SPV wallet like Electrum when the blockchain got too big. Maybe you bought a hardware wallet and moved your BTC offline. Maybe you sent some to Binance to invest in Ethereum at some point. There are countless reasons to shuffle BTC around - and countless reasons why you couldn't prove your full transaction history dating back to 2012 - none of which involve any crimes.
Has anyone ever been convicted for doing a few on-exchange trades and conversions? You should be keeping your receipts for tax purposes, it's on you to provide them up to a statue of limitations.
Or is this just a theoretical concern for anyone who isn't laundering Bitcoin stolen through ransomware or from exchanges?