I only assume it was Tesco because it was the last transaction on that card, as I remember at the time I was skint so had been unable to use it for at least a week so the minute I got paid, I went straight into Tesco to do much needed shopping!
Okay, playing devils advocate here, if I had a clone of your card and video of you entering your PIN to check your bank balance, I too would check you bank balance at regular intervals, and as soon as your pay went in, I'd go on a spending spree.
I'd suggest it far more likely that the culprit knew your PIN and had copied the magnetic strip or chip on your card while it was out of your possession and out of site at some point, or when it was passing through the card reader on a cashpoint.
Your bank would have been able to tell you how many times and when the balance were checked prior to the fraudulent transactions. And they would have been able to tell you if the PIN were used to authorise the transaction. But they have a vested interest in concealing how insecure plastic cards are, so you'd have had to push for real information.
Plastic cards are incredibly vulnerable, and the new 'contactless' cards actively broadcast your account information to devices in their vicinity when induced to do so. So if I saw you enter your pin, I could read your account information off your card by passing you in the street, and your bank would blame you, because they need to conceal these vulnerabilities from the public and protect themselves from having to shoulder the losses.
People need to protect themselves, but I find most people just think, "Ah, couldn't happen to me."