Whilst there may well be a multitude of reasons why the keyholder wasn't there at the correct time ...
The article used the word "forgot" in both the title and the text, so we have been given the reason. I'm sure much more sympathy would have been offered had it been "rushed to hospital" ...
It will be interesting to know what compensation claims come out of that one.
Not compensation exactly, but NCoC say you're entitled to a full refund of prebought tickets without having to pay an admin charge only if the train is cancelled or delayed. As the train ran on time ... admin fee is technically payable, but one hopes it would be waived in these circumstances.
Compensation terms seem not to cover the situation where your train runs, but you are prevented from boarding.
Again not compensation exactly, but advance tickets are "Valid on Chosen Train only. Non-refundable. Changeable for a fee before booked departure time" (
FGW▸ booking engine). National Rail says "If you miss the first train on which you are booked
for any reason, a new ticket
must be purchased." So - if you miss the train because you are locked out of the station ... again, one hopes that rule would have been waived!