Are you absolutely sure that it is not on your record?
Also, just an FYI- Institutional Action: Medical schools need to know if you were ever the recipient of any institutional action resulting from unacceptable academic performance or a conduct violation, even if such action did not interrupt your enrollment, require you to withdraw, or does not appear on your official transcripts due to institutional policy or personal petition.
If there is even a remote possibility that incident would be discovered, then you should discuss with advisors as to whether you should list it. It occurred as a freshman and if there were no others, it is unlikely to affect your app. Don't list it and it comes up, well, you are likely screwed.