While not quite the same my nephew while in home daycare at about 1.5yrs of age got so upset with the caregiver (who had taken a toy away) that he held his breath and passed out. The caregiver called 911 as the child was unresponsive.

He was perfectly fine. They ran a bunch of tests to ensure all was well. The doctor they saw at emergency said his nephew had done the same thing numerous times. It is just a thing that some kids do when really upset and there isn't really anything to do.

My brother and sister-in-law bought a LOT of flowers, chocolates, and wine that evening and brought it to the poor caregiver. She kept my nephew in care, it didn't happen again. This was 3.5yrs ago now and the same caregiver still cares for my other nephew.

You can bet the caregiver was nervous and worried for some time after. But, all was well.

Are you sure it was a seizure versus something similar? It does sound like a seizure but I don't understand why the child wasn't seen by a doctor after having what I assume was his first seizure. My nephew had like a CAT scan and other big tests done after passing out just to rule out a bigger issue. That seems odd to me that a seizure wouldn't result in some testing. But, I am not a medical professional. I would hope after a seizure there would be follow up to at least figure out why since it may or may not be a sign of a bigger issue.

I would just read up on seizures and have a plan in place (like what you did, calling 911) and keeping the child safe until they arrive.