What drugs don't show up on drugs tests?

Two nights ago I went to the bar and had 5-6 drinks. My friends confirmed this. That is the normal number of drinks I have and I ate the normal amount of food I usually do before drinking. Normally I'm completely fine after this many drinks. I left my drink with a guy I had just met and asked the bartender (who I kind of know) to keep an eye on it.

I don't remember much that happened after that but my friends said I kept passing out, threw up a lot, and was falling over. They called an ambulance bc they thought I was drugged. No drugs showed up in my tests but my alcohol level was 40.

What do you think happened?

What drugs don't show up on drugs tests?
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