3 months post op. One breast hasn't dropped. Will it? Should the doctor have lowered the crease? (Photo)

It is very difficult if impossible to change the crease. If it is attempted and fails - you will have a double bubble breast. You do have some asymmetry with this photo but may be caused by prolonged swelling. I would give it more time and consider self massage.

Ask your doctor about vigorous of breast implant displacement exercises and a pole wraps for the right breast to encourage dropping.  It is possible that the right side may drop further.However you had a significant asymmetry preop and most of the result that you see is caused by the asymmetry that you had before surgery.The problem with lowering the crease is the risk of bottoming out or double bubble deformity.  In my practice I would've recommended a unilateral breast lift on the larger lower side during the course of your breast augmentation.After 6 months of the asymmetry is still significant the better procedure might be to lift the lower breast to avoid the risk of double bubble or bottoming out by attempting to lower the right-sided crease.

It is really impossible to decipher what the issues are with your right breast at this time with a photo.  It just appears too high.  It may well drop over time on its own.  However, if not, it can be easily lowered to fill out the lower breast tissue and obtain better symmetry.  Lowering the IMF would not have solved this particular temporary issue.  Again, if it does not drop, it should an easy fix.