When I used to disassociate a lot I never remembered a thing - not anything during the time I was "away" or disassociated. I DO know when one of those episodes would start, though because I would start rocking, and then rocking harder with my hands crossed over my stomach. After that I was usually somewhere else, not knowing a thing about that blank space of time from when I was rocking to when I . . . "came to" I guess you would call it. When I was in a daze, it was usually the high amount of meds they had me on at the time (I had been misdiagnosed at this particular time of my life - very long story).
But heck, if you're feeling swirly and whirley in the head, I'd trust the T to call your partner or someone you both agree upon to come get you - OR, wait it out until you feel back to where you can drive - seriously. This will save both you and other drivers out there.
And believe me truly - I get totally what you are talking about when you don't want to give someone else your power, or let them have power over you or your life. I know this from experience which is a part of the long story I was talking about, above. No one will ever have power over me again - ever. But it sounds like your T is really looking out for you and cares about your well-being when it comes to your safety.
Be well, my friend!