OP, here is what I would do. The shop certainly doesn't want the authorities sniffing around (literally). You call them and say, "my minor daughter got sick from your little concoction. You can either give me the exact ingredient list and the proportions of those ingredients in whatever it is my minor daughter smoked or you will get to give them to the cops. I also want a large free sample to have analyzed if my minor daughter's doctors require it. You have 30 seconds starting about 25 seconds ago."
Better, do it in person. Have your cell phone in your hand and show the nice head person that you have already dialed 9 and 1. Be loud enough where all of the nice customers will scramble for the door like lemmings over a cliff.
Don't take no for an answer. If they start with "that dude isn't here", you say "Oh, so the only way he will come in is to talk to the nice officers? Okay, I am good with that." If they say they don't give samples, say, "consider it an investment in your long term business plan."
And then call the police anyway. Yup... you gotta. If they are mixing stuff that makes people sick, you have a responsibility to do so.