Prescription Drug Question

I'm sure this will get out of hand like usual even though it's not the normal question but I will try anyways.

So I was injured and received a prescription for a muscle relaxer that I know for at least me personally, I shouldn't of driven on that drug and I didn't drive. I had to do ride a longs where I was not driving for a few days after the injury due to company policy for any kind of injury and the fact that I just wouldn't of driven having while taking that drug whether it was legal to or not. They provide the ride a longs as a way for us to still make money after an injury while not driving which is nice.

So the question is, even with a prescription, is it legal to drive once you've stopped taking a drug that you feel unsafe while taking but it would still show up in your system on a drug test? I talked to our safety director about it and he felt the same as what I've always heard on here which is that the prescription would clear me in the case of a drug test as far as company and DOT policy. My biggest concern was less about my job but what would happen in the case of an accident. If I was involved in an accident say the first day I was back to driving and that drug showed up, I would think lawyers would have a field day with it even with a prescription. I guess my thinking was how would I actually prove that it was merely the remnants of my prior use of the drug left in my system and not that I was still taking it?

After bringing up my thoughts with my safety director as far as a hypothetical accident and how you would prove you weren't currently taking it, we both agreed I should just do ride a longs for a couple more days until the drug was completely out of my system. He said he really had never thought about it from more of the litigation side, rather than just company and DOT policy.

So what are your thoughts on this? Even if it is legal by DOT standards does that protect you in the case of an accident and some money grubbing lawyers get involved? How do you really prove that you are not currently taking it when is shows up after you've stopped taking it?

Like I said, I leaned on the safe side and didn't drive until I knew the drug was out of my system so I don't want to hear crap about how I abuse drugs, or I'm unsafe because I did about the safest thing you could do in that situation.