Nightly Rate Historical Data

We are unable to see the historical data with regard to the nightly rate at the time the reservation was booked.  We utilize dynamic pricing through an integrated partner, so the rates do change.  However, we are running into an issue where we cannot see the specific nightly rate the guest booked at.  This makes it extremely difficult to determine what they paid, exactly if a refund is due the guest.  We would like it to show exactly what the nightly rate was at the time of booking.