I'll try to help. There are some atypical features for herpes, but it still seems like a fair bet. Most cases of new oral herpes infection would be expected to have more throat and/or mouth pain from the start, either before or at the same time as fever; and diarrhea is somewhat unusual. On the other hand, the subsequent appearance of apparent ulcerations, including some on the soft and hard palate, certainly suggests herpes. Given the circumstances, I definitely agree you should be tested for HSV. But other viruses also might be possible and you need a throat culture for gonorrhea if not yet done done. Gonorrhea of the throat rarely causes such dramatic illness, but it's possible.
To the specific questions:
1) MedHelp advises forum moderators to avoid criticizing questioners' health care providers whenver possible. But if you are correctly reporting the urgent care doc's statement, I disagree. Initial herpes certainly can involve the throat and/or inside of the mouth, without lesions on the lips.
2) You definitely should be tested for HSV, as well as for gonorrhea and other viruses that can cause this sort of picture (coxsackie virus, certain enteroviruses). Do it soon; as time passes, a culture or PCR test for HSV and other viruses could become negative even if one of them is the cause. Re-testing for strep would also make sense; the previous test could have missed it.
3) You are correct; diarrhea is not usually part of the herpes picture. However, it certainly doesn't rule it out. Diarrhea sometimes is a nonspecific symptom that can be triggered by any severe inflammatory process; or as I said, some other virus might be responsible.
4) Herpes pharyngitis will clear up, with or without treatment, but without treatment it could take a couple of weeks. Given the circumstances, I believe it would be reasonable for you to be treated immediately with an anti-herpes drug (valacyclovir, acyclovir, or famciclovir), without waiting for the test results. If HSV is the cause, treatment will markedly speed improvement. (Unfortunately, there is no treatment that will do much for other possible viral causes.)
If by prognosis you mean the potential for recurrent oral herpes, that is more difficult to predict. If you acquired herpes from the oral sex event, most likely it is HSV-2; and there aren't very good data to help predict the likelihood of recurrent oral outbreaks in that situation. As it happens, another question on this forum came up just a few days ago. See
http://www.medhelp.org/posts/show/747691.
Bottom line: See another provider ASAP (or return to the same clinic with a copy of this reply!), insist on testing of your throat for HSV, other viruses, and a repeat strep test; and request a prescription for an anti-herpes drug.
Please return to the forum when you have the answers and let me know how things are going.
Best wishes-- HHH, MD