Ape wrote(in the theory archive: Is Sammael Dead?):

"Sammael is dead.
PoD contains a very definite piece of evidence mentioned casually in
conversation between Alanna and Cadsuane: 'He was injured, and then not, but I don't think a sister Healed him.' This proves conclusively that Sammael is dead. Reading the passage, it is obvious that due to the time frame, Alanna is referring to the wounds Rand received fighting Sammael (burning thread through the heel, etc), and that they disappeared without being healed by a sister or through natural healing. The only
other way that this could have happened is if Rand balefired Sammael
such that his wounds never occured, and Alanna merely remembers them.
Therefore RJ was clearing up the matter of Sammael's death, giving us
proof of it."

—-----

Until I read this I thought Sammy was still alive, but I think this makes sense (if Ape is correct).

1. Rand balefired Liah.

2. Rand's wounds disappeared as if Sam had been balefired.

3. No one else (that we know of) was around.

My conclusion is that Sammael used Mask of Mirrors (or similar) to look like Liah, and made a one power 'hologram' of himself by the Waygate as a target for Rand. I think he wanted to use misdirection to draw Rand's attack while Sam attacked from an unexpected place - or at least to make Rand freeze for an instant at seeing someone who should have died weeks before. Sam did not count on Rand's instant mercy killing and got his backside balefired. Sam having been toasted, Sam's hologram of himself also disappeared. Let me know what you think.