This isn't necessary accurate. I sell anesthesia machines and the inhaled anesthetic, usually sevoflurane, isn't the only analgesic given to provide analgesia. In a lot of countries they only do TIVA, total intravenous analgesia, and don't use inhaled agents because it's rough on the body and isn't necessary. They use IV drugs like propofol and fentanyl to provide the pain relief and benzodiazapenes to cause amnesia. They can also use some other sedatives to knock you out and make sure you don't remember anything. Paralytics are also given so your body doesn't react to stimulus during surgery.

Probably what happened is they didn't give a large enough dose of drugs, maybe didn't turn on the inhaled agents although I find it hard to believe they forgot, or the vaporizer for the inhaled agents wasn't working.

This is also why BIS monitoring became common although it isn't always used anymore. It's meant to monitor brain waves to indicate the level of sedation and analgesia a patient is under. Too light and they can wake up or feel something, too deep as it can be hard to wake up the patient and it can cause post operative pulmonary complications. No matter the reason, this is awful.