Because I am a authorized signer on my parents checking account, I have it set up so I get text notices of any debits over $150 (that is set by the user).  That way, if a weird large debit is started, I get two notifications, one 'processing' and a second when the transaction has 'posted'.   That gives me a short window to contest something, which I have not had to do yet!
Maybe there is something like that at your bank so you would be notified and take some actions.
My parents do no banking online so that helps.  This is just in case and it doesn't take any time to look at a text.  
Karl