First of all, downvotes are left at the discretion of the users. Nobody (including mods) has any knowledge of who downvoted or why except the person who cast the vote. There is nothing anyone can do about it. Are downvotes sometimes cast unfairly? Sure. But that's life. Overall, the voting on this, and all SE sites, tends to be quite valid, but yes, sometimes things go awry. File it under "people are strange" and move on.
That said, in your particular case, I can sort of understand the downvote. As you yourself pointed out in a comment, the file was actually there. So, either you missed it, or you were in a different directory or you were simply too tired and your eyes weren't working. That happens to the best of us, but it doesn't make for a very useful question for the site. While I personally would probably not have downvoted that, someone else felt differently. Or they were having a bad day. Or, perhaps, they hate usernames that start with the letter M. As I said in the first paragraph, this isn't something anyone can control.
So, just ignore it, there's nothing you or anyone else can do.