I've seen it happen myself a few years back...
Was on a train from Norwich back to Peterborough, and 3 times before departure there was an announcement to the effect of:-
"This is the xxxx train to LIVERPOOL LIME STREET, the train to LONDON LIVERPOOL STREET is on the next platform"
However, just after leaving Norwich, a "snooty" elderly couple stood up and asked "Does this train go to London??"
Somebody said, "NO, Liverpool Lime Street - it was announced 3 times"
Then then collared the guard (who was on his/her way down the train checking tickets) - and DEMANDED that the train reverse so they could get off....

They were advised to get off at Thetford, cross the road and catch the Cambridge-Norwich train BACK into Norwich and get on the RIGHT train!!!