There's quite a few of these posts about controlled substance agreements and urine tests in the past few days.
Read replies to these other posts -- there's advice there from a few of us.
In summary -- honesty is the best policy.
I can't give advice because I'm not a doctor (don't have enough patience). So, here's what I would do if I were in your shoes.
I would bring the Pain Contract with me on my next visit. If the doctor starts out with, "Unfortunately I have some bad news... we found Norco blah blah blah," I would simply explain how I was still having considerable pain, maybe my body isn't used to the oxycodone yet, etc., and then, like you said, point out that the Pain Contract didn't preclude this particular situation.
I would probably get the Contract, now, and put it in my wallet, so it doesn't look all fresh and new for the Doctor Visit Day (I wouldn't want to convey that I was feeling guilty about something I shouldn't be feeling guilty about by specially bringing in the Contract that day, out-of-the-blue).
That's what I would do.
I'm taking your post at face value. If your pain contract didn't address your situation (or was worded so convolutedly that it didn't make sense), I can't really find fault with what you did. Now, if your contract somewhere says that you must *only* take what you are *currently* prescribed, or if you broke your contract somehow, that's a different story.
I would only tell the truth, be straightforward and honest, and hope for the best.