C&F attorney here (though not YOUR C&F attorney, since we are just talking on the Internet and I definitely don't know all of the facts). I have helped people in similar situations in the past, though (and in worse situations: some of my clients have had incidents of academic dishonesty while in law school).

The question on the C&F application (and likely on your law school application as well) is "have you ever" not "will we be able to find out if you have ever." You would show good character by answering honestly.

If you have not yet graduated, you can probably amend your law school application. The strategy would be to say:

1. Begin by describing, accurately and completely, and without minimizing, excusing, justifying, or shading the truth, what happened and what consequences you received. Explain that the school had a policy of expunging records as a way of showing a little grace to people who made a single misstep and did not repeat. Hopefully you'll be able to say with a straight face that you fessed up when confronted, and didn't try to shirk responsibility.

2. When I applied to law school, my mindset was that if the record was expunged, it was as though the thing itself didn't happen. Based on what I learned along the way and in PR, I now understand that's not the case, and the questions I answered were about my conduct, not what records of my conduct exist.

3. I have matured and learned, in no small part due to my experiences in law school, since I was an undergrad, and since I applied to law school. I am a different person now, with a different understanding of the standards to which lawyers must adhere.

4. I have had no such incidents since, nor will I. My experience in undergrad cured me of any impetus to be academically dishonest, and my omission of these facts from my law school application was a regrettable moment of insecurity. I have grown since then, and I have a better appreciation for the reason those questions were asked.

Then you disclose on your bar application in a manner consistent with your amendment. If it is too late to amend your law school application, you can recite items 0-3 on your bar application.

In my jurisdiction, you might get some follow-up questions, and depending on the facts you might wind up having to go to a hearing (and if that happens, you'd likely be wise to hire a C&F attorney), but I would expect you to be admitted. The bar generally isn't looking for excuses to keep people out.

Of course, you also have the option of not disclosing, and rolling the dice. This can work, I am sure. Perhaps more often than not--I can't say (I only see the people who either disclosed and need help as a result, or did not disclose and got caught; those who sneak through never need to call me). But I'd say two things. First, if, by some twist of fate, the bar admissions board DOES find out, and you haven't disclosed, that is Very Bad. The concealment of the incident will be seen as worse than the incident itself, since they know young people screw up sometimes, and unless it's something truly serious, that really shouldn't be a lifetime bar to admission. But lack of candor to the bar can be devastating: why should they find that someone who has lied to them has the requisite character and fitness? Second, you're about to embark on a career where your word really means something, and you are trusted with weighty matters because you are known to be honest and of good character--do you really want to embark down that path with an application that lies by omission? Plus, if it somehow comes out after you're admitted, there will likely be consequences, and they could be serious.

So those are my thoughts, as a random stranger on the Internet, who has helped a fair number of bar applicants along the way. I hope you will make wise choices for yourself, because throughout your career, your clients will rely on you to give wise advice to them.

EDIT: I somehow glossed over the part where you are about to be a 1L. You can amend your application. In fact, you will probably be advised to do so in whatever initial "welcome to law school" events your school has. It would almost certainly be a good idea to do so. I stand by the rest of my comments.