I believe Tesla would be required to identify you and report all such sales (as they're >10,000$) to IRS i.e. not only IRS could ask, but it would be Tesla's responsibility to proactively report it as form 8300 for cash sales or something equivalent and ensure that your identity is verified, so instead of "no way for the IRS to notice that unless they audit you" this would immediately trigger an audit if you haven't reported your BTC investment profit as required.