Thank you so much for your attention to this, I am very grateful. Most cats will leave toads alone so we see this more often in dogs. Once in a while we see salivation in dogs who have ingested bees and presumably been stung, even though there isn't an obvious swelling in the oral cavity. I suspect this could happen in cats but can't remember a case. If the problem has cleared up and not returned, I would lean towards the possibility of an ingested source of irritation, even if there isn't anything that you can find that might have caused the problem.
Dental disorders can cause excessive salivation in cats.
Infected or damage salivary glands sometimes cause excessive salivation, as well. Other liver disease can sometimes cause excessive salivation so considering the possibility of liver disease is worthwhile if other problems haven't been found and the problem continues. If any other signs of disease do develop, such as fever, sneezing, eye discharges or loss of appetite and especially if the other cats start to show signs of this problem. This is the list of things that come to mind that cause salivation. Hopefully, the problem has resolved but if not, it would be a good idea to start looking for problems.