Are you a redhead? I kinda wonder if the same thing that causes anesthetic to not work as well perhaps does the same for other drugs?
If not, it could be something similar anyway - lots of drugs that totally mess with other people do absolutely nothing to me (Vicodin, Codine, sudafed, etc.) As someone who sees a lot of docs, has taken a lot of Rx (and a handful of recreational) drugs over the years that “should do x”, and knows a lot of people who are similar, I can safely say that every person experiences drugs differently - intensity, duration, effects, side effects, etc.
Just because you remember it, does not mean it wasn’t drugging, especially considering everything else. All super sus. I drink a ton (not a flex, I’m working on it and I’m doing a lot better!), and have never been even remotely paralyzed. Not once. I have given myself mild alcohol poisoning, while drinking by myself in my basement (very bad time in my life, and I lived alone at the time), have zero memory of the night past a certain point, and was sick for days after, but still woke up after a few hours with my head laying on the toilet seat in the 2nd floor bathroom, and crawled to another room and back to get a pillow to sit on.
Also something to consider is that he’s lying about his mom or the impact it has on him. If she is a user, it’s very possible it was through her or the people she knows that he got the hookup to get what he gave you. If he’s willing to rape, he’s definitely willing to lie.