Buprenorphine (Suboxone; Subutex) hangs out for a while in the urine. For a one time usage, I bet you'd be clean after 7 full days. It's a long-acting medication. Part of the perceived advantage in its usage as a maintenance medication is that it can be administered at large(r) intervals i.e. once per day. To give you a very basic idea, the vast majority of drugs are administered 3-4 times per day. Also, most drugs will be completely metabolized within 72 hours.
It wouldn't be strange for you to test positive after 7 days either. This is just a benchmark. In short, it's not a good choice for someone whose life entails random urine tests.
We typically don't allow threads related to drug testing. The reason for that is on display here now. We really can't answer your question in any sort of meaningful way, so we prefer just to leave the space open for things we can actually help people with.
4mg Buprenorphine in an Opioid-naive individual is enough to make a person sick for a good 24 hours or more. If you're taking it sublingually as intended, I wouldn't do any more than 2mg in a sitting and I would start with 1mg, waiting 20-30 minutes between dosages. Keep in mind, this 30 minute mark I'm speaking of is also just a benchmark. The effects of a dose are going to escalate slowly over the course of a couple of hours. It's only after 1.5-2 hours post-dose that you're really gonna have a good idea of what the next 24 hours will look like for you.
If you somehow end up insufflating the Buprenorphine, it's going to be at least twice as potent, so keep that in mind.
If you have previous experience with Opioids, then it's anybody's guess. If you're a user of Fentanyl or things of that nature, then your days of getting high on Buprenorphine are in the rear-view mirror. If you're totally naive to Opioids or basically so, then yea, if dosed properly, you could have a decent couple of experiences from that 4mg dose of Buprenorphine.