I am new to this but had a similar experience last year.
I had a weekly ticket that covered me on a paralel train line.
One day within that week i was travelling on a different train line and purchased a ticket for a single journey.
I got stopped at a station and asked to show my ticket.
I had lost the single journey ticket between the beginning of my journey and the end desitnation.
Paid cash for it so no proof of purchase,
I showed the inspector my ticket which coevered me for the paralel line which I thought may get me through.
Instead he said he woul