However I read this case report from 2016: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5308532/

Now I  realize case studies are basically the lowest quality on the evidence hierarchy. But does this not show that yes, the parasite can survive in the throat? Could it be possible that we just don't test for it orally much therefore it may be underestimated how many people are infected orally? Or is the evidence pretty clear that the it cannot survive in the oral cavity and more likely something is off/wrong in this study?

Thank you for your time.

My first thought is that I don't believe Dr. Hook or I have been quite as dogmatic on this as your question suggests -- at least I hope not. Probably there have been times when we didn't qualify statements that came across as absolute. The truth is (and remains) that oral Trichomonas vaginalis infection is rare if it occurs at all and that there are no known cases of it being transmitted by oral sex, i.e.oral to genital. If we said things like "oral infection is impossible" or "trich cannot be transmitted by oral sex", it was perhaps less thoughtful than it might have been. An accurate characterization would be that these things not known to occur, not that they cannot occur or have been disproved. The truth is more complicated:  oral trich has never been systematically studied and no STD experts that I know have ever seen a case that seemed to have been acquired by oral sex. I'm confident Dr. Hook would agree.

As for the case you cite, it's not just a case report (indeed a poor level of medical evidence), but a scientifically weak one in my opinion. I won't go into detail, but suffice to say they didn't test for the main causes of pharyngitis (various viruses), and imnprovement on treatment for trich (metronidazole) ignores the fact that most pharyngitis clears on its own over 7-10 days. There's no doubt T. vaginalis was present, but who knows for how long? We know that some positive results for other STDs (e.g. gonorrhea, chlamydia) do not reflect actual infection, but detection of a the organism in traces of a partner's genital fluids after recent exposure; or DNA from dead organisms that have been cleared by the immune system or never established themselves in that location. I'm not saying that trich didn't cause the patient's pharyngitis. But there's just no way to know.

Another report, which would better support the possibility that trich can infect the throat, was published 15 years previously:  https://www.ncbi.nlm.nih.gov/pubmed/11229850. In it, 3 men who have sex with men had trich in their throats. Based on a quick and cursory search, these are the only two reports I found in the entire global medical lliterature (in the National Instutites of Health's National Library of Medicine database) in which the title of the publication included both trichomonas and pharynx, pharyngeal, or pharyngitis.