I'm sorry to hear of your problem(s) and understand your frustration when doctors brush us off.
If you are not comfortable with your doctors assessment and have questions as to why a contrast was not used, and why your left leg is still cold, I would most definitely get in touch with him and have him explain these issues in far greater detail for you. I'd also ask what he planed to do about your left leg. That the LP came back neg. is great, as that rules out many things, but your leg is cold for a reason and he needs to figure out what that is. To just cut you lose does not seem right to me.
Talk with your doctor, and if I was in your shoes, I would be looking for a second opinion.
Have you been to the MS Forum here? I'm not suggesting you have MS, but those folks would be able to give you information I can't. They could, in fact, put your mind at rest.
I wish you the very best and that you find your answer.
Please let us know how you're doing, OK?
Peace
Greenlydia