[kgeist]

>the sequence τυγχαν may be the beginning of the verb τυγχάνω: “to happen,” or perhaps “not to happen.”

It says "me tunkhan..", which would indeed mean "let it not happen". Particle "me" means imperative "not". Or it can be part of a condition: "in case it does not happen..."

>there might be the beginning of διατροπή, a word found in other Herculaneum papyri that would mean something like “confusion, agitation, or disgust.”

But it could also be just diatropos - "various, diverse". "Diatrope" can also mean "shame" and "attack (of a disease)" (for example, diatropai nautiodeis - "nausea").