Because only Rand and Rahvin fought in the palace, the only bodies to be found (if there were any) would have been on the path they followed before going to TAR. Asmodean walked through that area but it had already been cleaned up of bodies (if there were any, Rand mentionned only the old servants during that battle, IRRC - and they didn't die). So yeah, his body left at the location of the murder would definitely have stood out when found.

Almost all the servants had fled. Hours after the attack, the Caemlyn palace was virtually empty except for Rand's people. The ones who were looking everywhere for Shadowspawn etc. were the Aiel, incl. the WO. The casualties were not inside the palace, they were in the Inner City, where the Shadowspawn fought.

It's not like "Natael"'s disappearance went unnoticed later. The Aiel knew. Whoever found him would have reported finding his body/a body. They all knew him, how he dressed etc.

So it's pretty safe to assume whoever killed Asmodean had the means to carry away the body, or destroy any trace of it.