I know where you're coming from friend, good on you for getting help.
I wouldn't worry about it.
Suboxone contains Buprenorphine and Naloxone. Naloxone's only in there to discourage abuse and I can't imagine there's any risk that they'd even consider testing for it.
Buprenorphine can be used recreationally, but it's metabolised into the opioid receptor agonist Norbuprenorphine. It's not a natural opiate nor does it metabolize into one and I'm 99.9% sure won't show up on a drug test for opiates or any other conventional drug test.
And even if it did, it's HIGHLY unlikely they'd test you for drugs, even testing for Marijuana would be pretty unlikely. I don't blame you for not telling them. But even if you did tell them, hopefully if they're reasonable they'll see you've already sought help for your addiction.
Try not to worry, if you don't tell them I can't see any way they would detect it in the off chance they even tested for drugs and on the off chance that test included a test for opiates.