My mom had an experiece similar to yours. I think her situation was due to what I called an over-dose of nitrous oxide. This was when I was in Jr. high school and knew nothing of the dental field. She weighs only 95 pounds, very petite. I think the dentist gave her too much of the "laughing gas" for her body weight. After the procedure was completed she couldn't get out of the chair. She sat there for nearly 30 minutes or maybe longer. She was very dizzy.
Its kinda funny because you just described the typical nitrous oxide sedation experience. Most people are fine with it, some even enjoy it a lot! Some of course do not and that's ok too. If you try it again sometime you might just ask for a lower dose. Nitrous is very safe so don't worry!