audiophyle is right. It's stays in your hair for a long time. Hair is like the rings on a tree, it gives a precise history of what you have been putting in your body. It really depends on how long your hair is as to how far back they can look.
I am not sure what kind of tea it is but a truck driver buddy of mine had to prepare for a test a while back and he found some herbal tea that moved to pot through his system in 1/2 the normal time (which is 30 days if you are a moderate to heavy user). Try doing a search on detoxifying herbal teas, you might find something.
I have also heard of people with very low amounts showing on their test results getting away with claiming they were exposed to very high levels of second hand pot smoke recently.
How much did YOU really consume, did you smoke a whole joint to yourself or did you have couple puffs off a community joint, chances are you didn't take in as much as you think. A puff every round doesn't equate to much. That's assuming it was in a joint form.