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I want to thanks all those who replied to my message

I got around 20 replies. Many just spoke about recent episodes, rather than
estimating a mistake RATE. Of those who tried to pin down the frequency of
"accidents", the answer ranged between "a handful of times in 5 years" to
"every 2 weeks or so". So I dont feel I am too out of range.

Unsurprisingly, eating out is quoted as the most likely occasion for an
"accident". Additional intolerances are also mentioned by many. There is a
"learning curve", with the frequency of accidents steadily decreasing.

Interestingly fatigue is mentioned as often as bloating, distension etc. as
the immediate clue that an accident has occurred. In my own experience that
was indeed the case in the first few years after I was diagnosed CD.
However, after a long episode of fatigue (due, as I discovered much later,
to gluten hidden in a medicine), I had a biopsy (in the UK) and I was told
that was OK. So, hopefully, minute quantities of gluten can cause
noticeable symptoms even without causing detectable damage to the
intestine.

Merry christmas!