Mine was used for a Netflix transaction in Canada. Monzo blocked it though as I already have one for the UK. There was another £15 transaction that I didn’t authorise that did get taken and it was an online one with ccv present.
After replacing the card and notifying me (I love how I had notifications a hour after the initial tweet from BA from my bank yet no email at all from BA) they obtained my £15 back.

Weirdly though it shows as £15 paid from BA not from the merchant that the card was used at. Talking to monzo customer service it seems they have a way to charge BA for the fraudulent transactions and deposit that money in the account rather than doing a charge back or requesting it from the merchant that it was used at (based in India and unlikely to give it back easily I imagine). This is a debit card so are charge backs not an option like on a credit card(? - I’m not too hot on banking tech and procedures)
Either way; Monzo sorted it all out quickly and got my money back directly from BA. BA were useless as expected and I communicated the above to the DM writer after verifying his account.