No, they lost themselves completely to something much less destructive than death. If a chemical causes a complete cessation of self it only follows that's brain death would as well, unless propofol somehow affects your ethereal spirit more effectively than your brain literally decomposing.
While I don't intend to make any actual assertions in either direction, I do feel bound to note that the experience of being anesthetized isn't really incompatible with a concept of souls and of ensoulment. After all, under anesthesia there remains something to "come back" to. When dead, not so much.
My theory is that death is different than taking propofol or some other anesthesia because while you are taking those drugs, your cells are still living. Your brain cells are not dieing and producing decomposition chemicals everywhere.
I think that's in the difference. When dead, your cells all decompose and start releasing and forming decomposition compounds which flood your brain and body. Not to mention your cells becoming fundamentally broken and unable to do their jobs.
My theory is that there's a fundamental system in the brain that gives us our sense of self gives us our sense of "this is me, and that is everything else". And that slowly goes away to the point where you can't distinguish the difference between self and other and you become everything.
Interestingly, entheogens as a category of drug have been defined by the same ablation of self/other boundary that you describe. (Please don't ask me for a citation! I remember seeing this definition in the context of MDMA's inclusion in the category, but have no idea where.)
