I believe the reverse is actually more common - mistakenly touching in with with oyster/contactless for a journey out of zone for which a specific ticket has be

I believe the reverse is actually more common - mistakenly touching in with with oyster/contactless for a journey out of zone for which a specific ticket has been purchased. I've done this myself a couple of times - touching in at my local station whilst half-asleep on a journey to Luton Airport Parkway when on my way to catch an early flight. What happens then is that TFL record an touch-in without a corresponding touch-out, and so might charge you the maximum fare for an unresolved journey. They're actually pretty good at fixing that automagically - so if, for example, you've not touched out at a station that had its barriers open due to crowding and make a return journey through the same station later in the day, they'll assume that you exited there and charge you the right fare. But if it's not fixed within 48h, you can claim a refund at https://tfl.gov.uk/fares/refunds-and-replacements https://tfl.gov.uk/fares/refunds-and-replacements