It's called a movie where things beyond realism can happen.

Who's to say that Morty doesn't exist? He could be some sort of paranormal being therefore, perfectly able to make things appear like the remote. As the other posters said, the "dream" was to teach Michael to change his ways. Morty probably put the remote there to prove to Michael that what he saw in his dream would happen.

But how exactly did the real, physical remote appear if everything involving it had happened in his dream? I perfectly understand your point and the message behind it, but objectively speaking, in the movie and its twist, it makes no sense whatsoever.

It's really not that difficult.
It wasn't a dream, it was a warning what could happen if he continued on the path he was following. Having the remote appear at the end and him throwing it away meant he learned his lesson.

Did you ever see "It's a Wonderful Life?"