...it does sound like tosh!!!!.... if a recalled item is scanned at an "epos" till then the computer recognises the barcode and alerts the cashire that the item cannot be sold ....this is why you were told at the till..... it sounds as if they have been recalled , and for some reason the water has been restacked on the shelf by mistake....this could have happened for several reasons, it could be down to unexperienced staff not checking the withdrawals sheet or it could be that new batches of water have started to emerge from the supplier but the computer systems have not been updated...
if it was not a good seller , then the epos system would not have stopped it being sold to you, infact it would be reduced for quick sale so that they could get a good seller on the shelves instead!!!....
...next time you are in your tesco ask at customer services to see the latest product withdrawals sheets(you may have to ask for a specific date rather than the item so try to think back to when they vanished) ...it is your right as a consumer. to be able to see this info...
don't be shy ...you are the customer and that's why it's called Customer Services .....
p.s I work for Asda customer services.....