The Lender has 48 hours to accept the request before it expires which means the charge is temporarily held on your card until the request is accepted or declined.
If the request is declined or expires, the authorisation on your card will be reversed. In the case of a reversal you won’t see a refund credit on your statement—you will just see the original authorisation drop off your statement entirely after a few days. There will be no payment, and no refund. It’ll appear as if the whole transaction never happened. Your bank should be able to confirm this for you. Depending on your card issuer, the original charge should disappear from your pending charges in the next few days. Whilst a rental is waiting to be accepted the authorisation on your card is temporary.