First, I'm sorry this happened to you.
You raise a frequently asked, important and intellectually fascinating question, about how we heal a traumatic event we cannot remember – in this case because you were drugged. But many traumatic events result in at least a partial amnesia, with or without date rape drugs. I think the answer is, we do similar things to what we would do if we could remember. You developed your own ingenious form of specific guided imagery to help yourself heal from your childhood abuse (brava!). This time you can use a more general guided imagery to help yourself re-regulate your mood states and get past this.
It's important for you to know that YOU DON'T HAVE TO REMEMBER THIS EVENT TO HEAL IT.
Traumatic memory doesn't sit in the cognitive, thinking part of the brain anyway – it's not a normal memory. It sits in the body, in the neurological wiring and biochemical responses. That's why your body is reacting with the intense kinds of biochemical swings, back and forth, between the alarm state biochemicals of terror, fury and panic; and the sedating biochemicals of alienation, emotional flatness and isolation. Those pathways are supersensitized from your past traumas, so it's no wonder all this got re-activated the way it did. You can deal directly with these internal swings, with what is happening with your body, and get to the same resolution.
Work with the Panic Attack imagery first, to re-regulate those wildly pendulating biochemicals; and once you're better able to manage and modulate these swings, you may want to work further and listen to the Healing Trauma imagery. Or, if that's too intense, something like Relaxation & Wellness, or Relieve Stress. The Healthful Sleep imagery might help too, if you're having trouble sleeping.
Physical exercise or moving meditation could be a big help too, as would expressing yourself through writing, art, dance or music, too.. Massage therapy or other forms of gentle body work from a trustworthy practitioner might be a good addition to your healing regimen too.
You triumphed before and you'll triumph again. Work through regulating your body, and use imagery to help you start to feel safe, protected and comfortable in the world again. But also try to stay away from those ugly predators, too!