Once I expressed an opinion on a question in a discussion with a person working on the problem. My opinion didn't work in its original form but could be modified a little to make it correct, i.e., although not completely correct it contained useful information.
Recently I found that the person I was having the discussion with has quoted me in a paper in an incorrect form by mentioning that I'd expressed the statement. But he has made no claims about its correctness. The person never asked me later for explanation and didn't even check if the way he is quoting me is correct. The discussion was brief and spoken. And he did not even send me a copy of his paper afterwards.
I feel that he should have asked me for clarification before quoting me in the paper or at least he should have given me notice that he is quoting it. At the time of the discussion he agreed to what I said and told me he would contact me about it and even send me a draft.
I don't like being quoted for a statement I don't know, and moreover I am a little bit pissed off by his action (quoting a brief informal discussion about a possible proof of some result without notifying me or asking me for clarification). What should I do now?
The paper is not published yet, it is on arxiv.org.
Contact the author first. Assume the best, that their memory is faulty, and suggest alternative text in a friendly manner. If you do not get a response, contact the editor of the journal they have submitted to.
Ultimately though a lot of people get misquoted, and a lot of publications get misunderstood & cited inappropriately. If it's really a big deal you might get a publication out of contradicting it, but otherwise just be glad that people think you are important enough to mention. It's better than not being given credit for your own ideas!