I am so sorry that your child might be using drugs. It must be a stressful time for you.
Yes, I would "snoop". And you are not alone. A lot of parents do snoop, and are concerned about the welfare of their children. Many of us have gone through this before.
If you think your child is using drugs, it is your obligation as a parent to search your house for drugs, including their room.
Your role as a parent is to guide your child to be a good or even great individual, while also ensuring that they are kept safe from harm and do no harm to others. When you suspect drug use, and do nothing, you are condoning it. What lesson is that for your child? I have no idea what drug it is, but if it ends up causing brain damage to your child, and you chose to do nothing, is that what you would want?
You also have a role to keep your family safe within the family home. If you suspect drugs are within the house, and do nothing, and then your son is arrested, how would you keep your family safe if the police have a warrent to invade your home. They will certainly not be as careful or as polite as you would with your property looking for drugs.
It's your home, you child and your family at risk. It's also your choice.
Yes, if your child catches you, there will be distrust, but stand your ground.
You also should monitor their web sites, their cellphone bills and text messages, and know who their IM and real friends are. Feel free to snoop if you are concerned.
But the best thing to do is prevention. Hopefully you and your child are working towards a great relationship so that your child can talk to you about their problems and you can help guide them.
Also, do not be afraid to insert yourself in you child's life. If you do not find any drugs, still talk to them about drugs. And if you find drugs, hopefully you have a plan for that too.
Here is a site you might helpful: Should I Snoop?