You can attend the closing and see the HUD 1 showing the payoff of the refinanced mortgage, and you can request to see that lender's payoff statement to be certain it matches. The QC deed is released to the closer, not your ex, to only be recorded upon payoff and disbursement.
In my state, for example, there is a State Transfer Return that must accompany any deed presented for recording - even on exempt transactions. If your state has anything similar, you may also be required to sign that, as well.