Dictionaries are descriptive, not proscriptive. It is possible for something to be correct, and dictionaries to have simply not caught up (or for it to be correct within a subculture the dictionaries do not cover). I agree with you that the former is not the case for "of" in place of "'ve", nor the latter in any subculture I am familiar with although that could certainly be my own lack of exposure. Regardless, it is worth knowing that many people will see it as an error and likely judge you for it.