Two things here.
1. Yes, any member of staff being asked about when the next train to X is should ask for a ticket these days, as the question is invariably actually "when is the next train I can use with my ticket". The passenger can always say "I haven't bought one yet".
2. As has long been my view, staff who are authorised to allow exceptions to ticket validity should carry a numbered pad to issue such authority (so any incorrectly given authority becomes an internal disciplinary or training issue), and it should never be given verbally.
It'll never happen, as then TOCs can't blame the passenger!
This is nothing new, I still have a TATT Pad, the last one I was issued was back in about 1985 - fellow old BR inspectors will recall them
This situation is often 'six of one and half a dozen of the other'. The traveller will be understandably annoyed by the cancellation and wants to get the next available train, the rule is clear as others have pointed out, unless specific instruction to the contrary is given, then the ticket will be valid on the next train of the same company. ( I don't particularly like that any more than others, but we don't have a national rail company so we have to live with it.)
If a member of staff is asked, the traveller should always show their ticket to get confirmation that it will be valid for what they want to do. Being pro-active in this will benefit the traveller in pretty well every case.
If the traveller does not show a ticket then the staff member must ask to see it so that they can give accurate information and I've always instructed staff that it is better not to give any information that might be inaccurate, so that's why they must check the ticket. I have also always advised that the staff member should write their staff number and location on the back of any ticket to show that they have authorised travel
That said, if it is clearly shown that a staff member has given wrong information when asked and said 'yes, it's ok' when it was not, it is still an authorisation and the ticket should be accepted as valid..
On the subject of the guard calling Police, there may be legitimate reasons for this action.
If the traveller did not have a valid ticket and a fare was due, but the traveller refused to pay that fare, then as long as the staff member had explained that alleged offence, under National Railway Byelaw 23, the traveller is obliged to give their name and address.
That was all the guard needed to do. So long as correct details were given then the guard should put a note into the company who would write to the traveller about the fare if no authorisation was in place, but given the circumstances would more likely take no action.
If a traveller has no valid ticket, refuses to pay and either refuses their details or gives false details, that's a whole different ball game and can result in prosecution although a Police presence is not always necessary in such a case. Clearly, if staff had given wrong information and if a traveller held an invalid, but authorised ticket, this would not ensue and if everyone adopts a commonsense approach, the risk is avoided.