Sent money to the wrong bank account? You’ll soon get more help getting it back

jonesMUFCforever

They are indeed obliged to seek recovery on your behalf but this is on a best endeavours only.
If the sister does not return the money then yes it is lost because the bank is not liable for something they have not done.
An example is - if you lost your purse just after withdrawing money would your bank be liable to refund you - I think not - this is the same.