I lost 2 reputation points because a question was removed. I didn't asked that question. So these are my guesses:
1.-I gave an answer to that question.
2.-I edited that question.
3.-I upvoted that question.
But I can't remember. Its not the only one. I have got this like 3 times total. The reputation help page doesn't say anything about it https://stackoverflow.com/help/whats-reputation
What is the reason? and someone should totally add that to that help page :)