Also go to drug store and buy a five panel urine drug screen. It will tell you in moments if they are using oxy, coke, heroin, weed, or meth.
Maybe they are smoking some other drug than oxy. The bottom line is they should not be swallowing oxy much less snorting or smoking it.
Make them take a pee test. If they refuse they are guilty. This is very important what I'm going to say, you must at all cost observe the urine leave their body into sample cup. I have taken my fair share of urine drugscreen and passing them because I submitted synthetic or someone elses urine. If they don't let you watch then they are hiding something.
You can buy such test at most drugstores for about $30
In a pipe like a weed pipe or on tin foil, check the trash containers. Have they been isolating more than usual? Changing any habit, ie, sleeping more? If they are high on oxys their pupils of their eyes will be very tiny, they call it "pinned" a telltale sign. Talk about it with your child, Keep the line of communication open, and good luck with it.
I've heard they smoke them on aluminum foil and it leaves black lines on the foil like char marks. If you found lots of balled up foil in the garbage that would be a big sign.
Are they nodding off and looking "whacked out"???