There is NOTHING worse than your child coming up missing, even for a few seconds. Your reaction sounds like a pretty normal parent reaction to the circumstances.

My son disappeared at an outdoor theater program in Houston for nearly an hour. The police were called in to search for him. Having to hand over a picture of him to the police was traumatic. He was found safe and sound (and he never knew he was lost; he had wandered over to a playground nearby; he likes to tell us he knew where he was the whole time -- turkey!!) Anyway, it has been 12 years since that event and I still get sick just thinking about it.

My point is, a meltdown under your circumstances today is completely in the range of normal. Your stomach will stop doing flips eventually. Glad everything turned out well.