I can't give a precise answer to this question because I don't have either the technical knowledge of how Trainline and Apple Pay work, or the legal knowledge about whether TIL would be able to obtain this information from Trainline. But I do know enough about the law to know that when suspected crime is being investigated, the investigators have very wide powers to obtain information.
So it isn't safe to assume that something that you've done won't be uncovered, and there is an obvious downside to denying something which the investigator can prove happened. This means that if someone (let's call them X) has done something which they hope an investigator won't uncover, then essentially they have three options
- actively deny that they did the something: if the investigator has no evidence of the something then this may put them off. But if the investigator knows that the something did happen, then they also know that X is lying, which means that they've got reason not to believe anything else that X says
- don't mention the something: again, this doesn't draw it to the investigator's attention - but if they do know about the something then this may raise doubts about how much X is engaging in the process '(X knew they did something: why didn't X tell us? Is there anything else that X is hiding?')
- be open about what has happened. The bad news here for X is that it may bring things to the investigator's attention that they didn't know about, but the good news is that X is clearly co-operating so that there's no reason for the investigator to think that there's anything they don't know about.
None of these options are great. But to my mind, being open is the least worst.