Pay him/her for an hour of their time. Say this "I have a friend who is doing something that worries me..." then explain that "he" hobbies. Pay in cash, too. The lawyer will know exactly what is going on, but the job is to pretend they don't, so no problem and no need at all to be more discrete or creative.
The lawyer will first say that you should tell your friend to stop breaking the law, and then explain what you need to do if you are busted, and suggest that you always keep their card in your wallet.
Whether you actually go to see a lawyer, the answers to your questions are:
1. Keep your mouth shut. Express surprise and confusion and ask to call your lawyer.
2. Keep a lawyers card with you at all times, and when confronted by LE, call that lawyer as soon as you can.
This is true in most cases with LE - if you happen to be in the wrong place at the wrong time, no matter how totally innocent you know you are, see a lawyer before you talk much. I would tend to listen, maybe say a little if it is a situation where I genuinely have no idea what is going on and was not doing anything illegal, but that can be risky. Always safer to shut up and lawyer up.
Yes, there is a high likelihood your name will be posted publicly by LE, so you should also work on an explanation for that. Not that there is a good one. But if you shut up and lawyer up, the odds of you being convicted of anything are very low.
Not a lawyer.
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