Essentially non existent
There have been no know transmissions of hep c in the manner you have described.
Hep C is a blood borne illness hepatitis C infected blood must enter the bloodstream of an infected person.
The most common method of transmission is sharing of IV drug needles or having a blood transfusion prior to 1992 when testing for hepatitis C antibodies was developed and the blood supply secured.
Other methods of transmission would be participating in extremely rough sex acts where exchange of blood could occur ie BDSM or blood sports. There is approximately a 6% risk of vertical transmission from mother to child during the birth process so being born to a hepatitis C infected mother would present a small risk. Receiving a tattoo at an unlicensed facility is a small risk. Also sharing of personal hygiene items like toothbrushes, razors or fingernail clippers could also present a small risk.
From the US CDC
“ Hepatitis C is not spread by sharing eating utensils, breastfeeding, hugging, kissing, holding hands, coughing, or sneezing. It is also not spread through food or water.”
You have a lot of what if’s in your question.
IF they had hep C being the biggest as only about 4% of the population has hep c
IF there was blood in their mouth. Doubtless if there had been sufficient blood for transmission you would likely have tasted it as it would require a very large quantity of blood to have any possibility for hep c to be transmitted in this manner.
IF you had mouth sores one would think you would be aware if you had fresh open weeping mouth injuries. Again you would likely be able to taste fresh blood in your booth from such injuries.
For transmission to occur it would require an open wet/weeping injury for the hepatitis C virus to have any possibility however remote of being able to enter your bloodstream.