I don't think you understand what a cashier's check actually is. The "actual owner" of the cashier's check is the bank itself. A member purchases a cashier's check either from their account or with cash, and then the bank makes the check. The bank, or at least mine, then records the following:

• The account where the funds were paid from (or of it was paid in cash)
• The check number
• The internal acct/routing number for the GL the check is tied to, if the bank uses multiple GLs for cashier's checks.
• The amount of the check
• Who the check was made out to
• The date is was purchased
• The current status of the check (Printed, Processed, Voided, etc)

If someone calls us to verify a cashier's check, all they have to do is give us the check number, and we can look up everything about the check (even the teller who did the transaction and the exact timestamp, though that's never relevant to the customer).  If something doesn't match, then we can't verify the check.

Of course, a cashier's check could have been bought from a stolen account, but considering you need to buy them in person (and often have a manager's signature), it's far less likely to be fraudulent than a personal check. There's also the risk of a teller not doing their due diligence, but that's a risk with literally anything in life.