Meth/MDMA interfering with the contraceptive pill

My question is whether anyone has experienced or heard of anyone that had the contraceptive pill failing on them as a result of meth or MDMA use?

Have you done a search of the Health forum, by the word "contraceptive"? I think you'll find that this question has been asked a hundred times.
Try looking at this thread;
Health Mini-FAQs

The only way that drugs will affect the contraceptive pill is if you take them so much that your body breaks down, if you lose too much weight (have less than 10% body fat) from drugs or any reason at all, you will stop having a menstrual cycle altogether and wether you get it back or not is a luck of the draw situation, you could remain sterile. Having almost been in this situation myself really opened my eyes so watch your weight if you are a regular user of drugs.
If you notice that you have been spot bleeding or anything strange in your cycle after taking drugs, then just be really careful and take extra precautions until your cycle is normal again.
if you have a doctor that you trust, tell them about your drug use, dont hide details from them that could end up saving you from harm later.
Andromeda

Andromeda: losing weight while taking the OCP should't stop you getting your period. The period you get while on the pill isn't a real period - it's a withdrawl bleed. Therefore, there isn't a normal menstrual cycle for weight loss to interfere with, as the cycle is dictated and controlled by the OCP.
If you were not on the pill and stopped menstruating because of being underweight, getting back to a healthy weight should restore normal menstruation and fertility.