It is actually atypical to pass out from fear, as one's blood pressure usually rises, not drops during panic.
Beyond that, since you were in the car and seated....this lessens the chance of fainting even more.
(however, if you are ever in the same situation, pulling over and putting you heads between you knees...or lying sideways with your head level to your body will help the faint feelings pass)
Bottom line, feeling faint from Anxiety is common...actual occurance of syncope is not.
Practicing coping skills...especially breathing exercise to reverse hyperventilation is key...so be sure to work those daily!
Great job on pushing your comfort zone boundaries. Today's experience was just a small detour along your recovery path...just hop right back on.
Keep us posted so we can keep you in support!
"Courage is not the abscence of fear, it is feeling afraid and doing it anyway!"
"Worrying does not empty tomorrow of its troubles...it empties today of its strength."
Corrie Ten Boom
Panic Syndrome recovery due to CBT