I one time thought Flame was dead because she was laying with her head and neck out of her hide, like she always does when she is hanging out in ambush mode 80% of the time, but she was laying like dead weight with her head resting completely on the substrate, out in the open in broad daylight. I had to poke her like 4 times to check if she was dead before she finally woke up!
Ever since then, I can usually tell when she is sleeping because she completely lays relaxed on the substrate and her head is just like dead weight laying on s pillow.