Not a math question. OP should perhaps ask this in a community for English language learners.

I disagree. It strikes me as akin to meta-statements like $A\to B$ versus $\left(A\to B\right)\to C$. I think it would also be on topic as an English usage question (no need to impute learner status to OP), but that doesn’t invalidate its presence here.

I don't think being akin to a statement in predicate logic is sufficient to make a question on topic for math. Contemplating the mortality of Socrates would also be off topic, unless it was specifically asking about applying modus ponens or something. Likewise, I think it would be okay if OP were using this example to ask about rules of probability in modal logics and the difference between $P(\phi)$ and $P(\Diamond \phi)$, but as written that isn't the question. The question is about how to interpret an English phrase differently if the words ‘probability that there was a’ are present, which only incidentally references mathematical content.

(OP is not new to this site and they have previously established that English is not their first language, not that this makes a difference to how on-topic the question is.)

Of course it’s not sufficient. My point was only that the question lies somewhere in the intersection of maths and language. It raises some doubt (in contrast to simply saying “Not a math question”), and I chose to give OP the benefit of that doubt.

Other parallels:

① Verizon’s conflation of “point zero zero two cents” and “point zero zero two dollars”—I would consider this on-topic.

② Lewis Carroll’s Mad Tea-party and taking “more” than nothing—I think this is a marginal case, leaning towards being off-topic.

③ Also from Lewis Carroll, his “the song’s name is called”—I would definitely consider this off-topic.