A lot of us forget that riding a scoot is not the same as driving.
Riding requires that you be much more actively engaged before and during every moment of the ride.
You need to make sure your gear and scoot are in good nic, and then once you set out, you need to actively use your body to set up for every turn and constantly perform active scans of your surroundings to check for cagers who present a potential danger to your continued existence.
Driving requires a much lower level of preparation and concentration to do the minimum that will allow you to arrive safely at your destination. In fact, driving requires so little of your full attention that you can listen to music, talk on the phone, carry on a conversation with other passengers, think about problems at work and what you need to pick up on the way home for dinner... and still not feel you have endangered yourself or others.
Because the bar is so much lower while driving than with riding, and because we tend to (mistakenly) treat them both the same, it is confusing and scary when we have an attack of uncertainty such as you described. After all, most of us haven't had such a panic attack while driving since we were 16, right?
That attack you had is your subconscious screaming at you that you are not focused enough for the task at hand. It is waving a red flag to get your attention so you will realize that either you need to get your mind in the game or leave the scoot and take the bus/tube today.
No shame in that.
There are days when you simply don't have the head-space to handle both life
AND riding. Not everyone has a well developed sub-conscious status panel to send up a warning flare when we've exceeded our mental bandwidth.
Knowing you to be an organized, responsible person, it is not surprising at all that, even when preoccupied with a million and one other things, your subconscious mind still felt responsible enough to let you know it wasn't up to keeping you safe on the road.
As unsettling as it may have been... IMHO, it is a good thing to have happen once in awhile.