Hello doctor; can someone be falsely tested positive for buprenorphine without taking any drugs?

Depends on the type : Of test. Screening tests are set at high sensitivity and often have false positives. If the results are to be used for medico-legal purposes, a clear chain of custody needs to be maintained and screening results need to be confirmed with a different assay.

Rare in urine : Of thousands of qualitative or screening urine tests, i don't recall having seen a false positive. False negatives: many times. The quantitative or confirmatory test uses lc-ms technology which has a high sensitivity and specificity. But anything (almost) is possible.