I used to miss constantly, and honestly I could never feel them, ever. Also, unless you were hitting a deep vein, it more than likely would be the equivalent of subcutaneous type route of administration, the tissues absorb it before it can get through the fascia to the muscle.
I was never a huge Cocaine user, but I found IM injections could last 45mins to an hour. Again, I think my relative inexperience with Cocaine plays a role here. Most others I've talked to say 15 - 30 mins, but this is my experience.