I don't doubt your account, but that wouldn't make my own odd - it's merely a case of varying experiences
What we're interested in establishing in this thread, so far as I can make out, is some insight into whether we punters find that "unannounced/unasked for" attempts do happen, and, if so, to what degree, allowing for, as LLP suggests, probable selection-biases. My own experience, in neither routinely or actively selecting for it; nor, so far as I can tell, cleaving to any wildly unusual punting pursuits, is that 1/ yes, it does, and 2/ a significant minority of times- and a good deal more than others seem to entertain as possible, or matching their experience.
One obvious prospective blind-spot is that, in my observation, it's on the whole more likely to happen with repeat visits (though there have been exceptions), and so, in the case of one-off visits, we're less likely to encounter it. One-offs account for something like half of those I've seen, which suggests that I might be underweighting its prevalence.
