Following the thread's shift away from the OP's report to more general situations . . .
Anyone discussing this ever bought an advance ticket online? There's a little box and link that has to be ticked to say you've read and understood the terms and conditions, and furthermore by ticking the box and clicking continue/purchase, you agree to be bound by them. That's the point of no return. If you don't like it, or your plans are not concrete, don't buy the ticket and complain later. You've already agreed to pay the walk on fare being charged if you board a different train by ticking that box. There's no grey area, just black and white
Well I guess I've found myself in this situation on several occassions over the years, though never felt any urge to complain about it. Its just a consequence of circumstances which I hadn't forseen - and yes, of course, if they had been reasonably forseeable then I wouldn't have committed myself to an advance ticket by ticking that box. That's what is meant by reasonably foreseeable!
I gave an example a few posts ago where the unforseen element was a track circuit fault affecting my local connection to the mainline station - other posters have give other examples, each with different degrees of responsibility of the traveller for the change of train. To be clear, I am
not complaining that I have to pay again if I find myself wanting to travel on a train other than the one I had hoped to travel on.
But the point which I DO feel justifies a different policy on advance tickets which have become invalid is that they need not become absolutely worthless at a stroke. I don't think it significantly damages a TOCs revenue to allow a ticket to retain some residual value which could be of assistance to a passenger with altered circumstances.
Sure, we don't want rail staff to have to judge what circumstances might justify a residual value and which don't (tho' they seem to get such stories every day whether they want to or not anyway!).
So I would feel happier if a ticket simply retained some percentage of its face value for travel on comparable services, enabling them to be excessed up to the required value for the actual journey.
Its not for me to do the sums for the TOCs so I won't pretend to do so, but I guess there's a point up to which they would benefit - maybe not from much extra travel, perhaps from more willing and pro-active buying of excesses, but hopefully less of the "surprise" by passengers (genuine or faked) who are told their ticket is invalid. And less of the hard-done-by attitude of some passengers which is as much a consequence of the application of the T&Cs as they stand as it is a consequence of people attempting to travel with invalid tickets. (and being annoyed when they are prevented from "getting away with it").
People more knowledgeable than me might criticise some consequences but if I confine my proposal to just circumstances in which an invalid ticket might be presented and still have a residual value which can be excessed then they would be where a passenger is attemting to complete a journey as similar as possible to the one for which they hold the ticket. And where the variation to the time, route, TOC or whatever is comparable to the variations which the TOCs incur during times of disruption (and which the passenger accepts as variations to the service arising from circumstances which the TOC had not forseen).
In my own case, where buying a second Newcastle-London or Edinburgh-London ticket at walk-up prices at a significant cost, it would give me some more confidence to travel if my ticket went towards, say, 25% of the cost of an alternative service.
Finally, there's a lot of talk on here about "fairness" which doesn't impress me much - but there is something equitable about ticketing T&Cs which anticipates that unforseen alterations may delay (or cancel) services, and which also acknowledges that the unforseen can strike a passenger too, and that a committment can be varied within reasonable and understandable limits by both parties to the contract.