What is used for euthenasia? Yellow liquid? How much should be used?

Okay, so I'm panicking a little now. I'm sure that I'm just overreacting, but maybe someone can just put my mind at rest?
My dear Willow was put to sleep on Monday. She was given just one injection after the insertion of a cannula (done in a seperate room, so don't know if she was given any kind of anesthetic while away from me - she was so quiet at that point I couldn't tell if she'd been drugged or not). She was given a yellow liquid. I would have said a fairly small amount too, but then perhaps rabbits don't need as much as I would have anticipated. She was gone very quickly and the vet did check for a heartbeat. She had a few muscle spasms which the vet said was probably due to her suspected neurological problem.
My parents took her to be cremated yesterday afternoon. They were about to close so I assume it would have been done today (we have to pick her up on Thursday - seems like a long time to me :?)
I couldn't bare to look at her after the vet wrapped her up. However my parents both checked a few hours later. They were a little surprised that she still felt warm and phoned the vet who said it was normal. My parents told me she had started to go stiff, so I assumed that was rigor setting in. I will ask my Mum more about how she looked again when she gets up tomorrow.
But I'm now panicking - she was definitely gone wasn't she? She certainly looked it the last time I saw her. But I haven't seen any reference to a yellow drug being used online, except as a pre-euhtenasia anaesthetic. My Dad told me it was another colour when our dog was put to sleep (can't remember if he said blue or pink now).
Please tell me she was gone. I can't bear to think she may have just been in a deep sleep and undergone cremation today.. Please...
Edit: I've just managed to catch my Mum and asked her. Both she and my Dad checked her multiple times and she says she's 100% certain she was gone.
I guess I'm just panicking..

I am sure that Willow had passed within seconds of the drug going into her bloodstream. All that Willow was to you remains with you. Her body was just a vessel that contained her soul during her lifetime. That vessel became aged and frail, unable to go on. Her soul now lives within your heart and within your memories. There it will remain. The love we share with are Soul Rabbit can never die.

I dont know if you have read the words in my signature. Here is a larger image, I think it is true when referring to our Soul Rabbit

Thank you so much, Jack's-Jane. That was so comforting and very beautiful.
I guess I was just panicking. I'm really sorry to bother you all with another thread.
But losing her was bad enough. The thought that maybe she wasn't completely gone really panicked me. I'm usually very rational... Until in concerns my bunnies. Especially Willow.
I miss you, my beautiful girl

Rabbits are a lot smaller than a dog and have a faster metabolism so the drug amount is very different. Even an anaesthetised rabbit would have a heart beat the vet could hear with a stethoscope. She was definitely gone.

I had a guinea pig die of a heart attack at home once, and I took her to the vets to be cremated on the bus. It was awful - I kept finding myself checking she was really gone, because she felt so warm in the box. So I can understand what you mean.

she would of been gone as others have said, try not to keep going over it in your mind I know its hard, hour after my sox had died he was still warm and only his legs had gone into rigor, his tummy was so warm I stroked it and cried, even myself thinking are you sure your not just sleeping, but he had gone to the bridge, he wasn't put to sleep as he died at the vets, but they just look so peaceful, like they are just sleeping

sorry for your loss xxx

Thank you all so much, you've really put my mind at rest.
Again, I'm really sorry to bother you all with another thread. It was really playing on my mind last night and I really began to panic.
Losing her was painful enough, but the thought of that...
Thank you all so much. You've no idea how much that has helped me to put my mind at rest.