It certainly happens, very occasionally, here in the UK. You try to pay something with contactless but there's a long processing delay. The terminal will then time out and ask you to insert the card and enter PIN, and you will get something strange printed on the receipt like "CVM: offline PIN". You may then see the transaction pop up in your notifications a few hours later, or early the next morning.
Also, some merchants do offline or semi-offline transactions as a matter of course. London Buses, for example, accept contactless payments via bank card. But the transaction must be processed very quickly and the mobile data connection is not entirely reliable - the bus could be in a tunnel or a coverage black spot. So what really happens is the transactions are batched and processed at the end of the day (this also allows them to do some post-processing for multiple-journey discounts, daily price caps, etc).
Someone like London Buses isn't overly concerned about fraud because the transaction values are low. But they do have a way to blacklist cards numbers that are known to be bad.
Also, some merchants do offline or semi-offline transactions as a matter of course. London Buses, for example, accept contactless payments via bank card. But the transaction must be processed very quickly and the mobile data connection is not entirely reliable - the bus could be in a tunnel or a coverage black spot. So what really happens is the transactions are batched and processed at the end of the day (this also allows them to do some post-processing for multiple-journey discounts, daily price caps, etc).
Someone like London Buses isn't overly concerned about fraud because the transaction values are low. But they do have a way to blacklist cards numbers that are known to be bad.