Does flurbiprophen & lidocaine in a topical pain cream show positive on a employment drug screen?

Possibly: some NSAIDs can give positive tests for THC on screening tests. Lidocaine will not show up as Cocaine or anything else. However, screening tests should be followed by more sophisticated confirmatory tests that will be able to detect the difference. If they are not doing those tests, they are not following usual procedure, and you need to ask them to get confirmation if you have a false positive.