Tell the guests that if they leave it in this hotel, they will find it for them.
Please leave your contact number and call him back if you can't find it.
First, contact the front desk immediately to see if the restaurant waiter gave it to the front desk.
If not, contact the supervisor or manager of the restaurant on duty immediately to see if any waiter has seen the guest's wallet.
If you do leave it in the private room, please ask the guests to pick it up the next day. If the hotel level is ok or the guests are more important, you can send people from the team to send them to the guests.
If you can't find it, you must apologize to the guests.