As I keep saying on various threads of this type, we can smell the fear - we can usually tell when somebody is lying...
The last one I had boarded at Paddington (unmanned platform), told me he had left his ticket in the bag on his bike (I walked up to check the bike shed - no bag, or place to attach it), he then says he must have dropped it, he then says (coming from London to Reading) that he has no money, card, ID or indeed wallet at all. He then gives me an address that is miles away from Reading, much further than is reasonable to expect him to cycle. So I figure that my Revenue colleagues are better placed to check out the address than me. So I ring them, but they ask BTP to meet.
His whole body language, and story, did not check out. What should I have done - waste time giving him a UFN that I am 100% certain would not have checked out, and let him have a free ride next time? If he was genuinely stuck, he could have done a SILK before boarding. Now, he is in the system, at the least he knows that it's not as simple as getting on a train and giving any old BS, which we will swallow in the name of "CustomerService".
For every genuine person who has lost their ticket, there are a dozen who will use it as an excuse when caught. Just think how many turn up here with stories that don't add up even when there is time to think about them. I work on the principle that if it doesn't sound logical it probably isn't true.