You had no risk at all for hep C.
Hep C is almost never transmitted sexually, and when it is, it's almost always from unprotected anal sex. The main way it's transmitted is sharing needles for drug use, contaminated needles or other equipment used in tattooing, etc. It is only found in blood, not saliva or semen, etc.
https://www.webmd.com/hepatitis/hepatitis-false-test-results#1 - The test may mistake HCV antibodies for those for lupus, rheumatoid arthritis, and other conditions. You don't say why you were taking the Etroicoxib, but I wonder if maybe the condition you were taking it for is causing the indeterminate result, rather than the medication. If you have one of these conditions, you may always get these results on a hep C test, or a false positive.
In any case, a simple hep C viral load test will determine if you have it or not. They may not suggest it since you had indeterminate results, but I'd push for it if I were you, if you had any kind of risk prior - sharing needles for drug use, have tattoos, etc.
You had absolutely no risk for any STDs from the encounter you describe.