If they gave you the laptop, I'm confused as to why exactly they would care about reformatting it. I'm technologically illiterate but my understanding is that it's sometimes necessary when your computer gets viruses or the like.
Need more information, your story doesn't seem to make much sense. How can you (or why would you) reformat something you never use? On the surface, professionalism citations are definitely red flags for applications. If you can't handle medical school rules, why should a residency expect you to handle theirs? This one seems silly, but it also doesn't seem to make a lot of sense. Also should you receive said citation, your attitude towards it needs to do a 360. Own it, apologize, and state what you learned from the incident. Regardless of how silly the actual incident is, let residencies decide that for themselves based on your description.
As a measly pre-clinical medical student, I don't know nearly enough about the process to comment intelligently. If I had to speculate wildly, I'd say that if it's actually what you described and there isn't something more egregious to the story that you're leaving out, it should be fine.
So how did it get reformatted? I'm no tech expert, but as far as I know, they don't just reformat themselves. This e-mail was after you turned in the laptop? I'm sorry, but your story still makes no sense and if you approach a residency with that story they will have tons of questions and many will likely pass on you rather than try and sort out what the heck you received a professionalism citation for.