As others have said OP, it's not a mystery. Particularly given the shifting timelines around Covid, it is entirely possible to confuse and misremember dates, and genuinely believe you knew about information earlier than you did. It's happened to me, notably regarding work.
I appreciate you say you have written notes that corroborate your account, but there are many timelines around reporting on Covid (I'm in Ireland, I checked now, and the first reporting of a 'mystery virus, believed to be a variant of SARs' [so no mention of Coronavirus, and obviously the use of Covid was much later anyway), was on 16 January. All discussions at that time talked about a 'pneumonia' that was causing some concern. There was no reporting about this sooner than January.
The idea that the parents were concerned and worried about a school trip in December is not possible, at least not in relation to this matter - perhaps otehr concerns unconnected to COVID were at play?
I am reading a book about the way Covid was handled in Ireland, and repeatedly, I have stopped and been amazed, and nearly wanting to contradict what was in the book e.g. regarding the timing of certain restrictions, dates of return to school etc. I have 3 kids, and work in a university, and could have sworn to specific timelines about home schooling / education, or when we opened up campus and so on.
Our minds are very powerful and there is a huge fallacy of memory. The reality is that the 'news report' you imagine seeing did not happen, whatever you believe your diary entry to reflect.