If someone ends up in the hospital once from a high blood sugar, could that have caused brain damage to the amygdala?

Unlikely: If it was just high blood glucose, it is unlikely that it would cause a vascular event, like a stroke or tia. If you were severely dehydrated, in ketoacidosis, in shock, or otherwise severely ill, then it is more likely, but you would have probably had neurological symptoms at the time.

Amygdala: A single hospital admission for high blood sugar would not likely cause damage to the amygdala.