What could cause that to happen?
Have you moved HL2 and the episodes to the SteamPipe beta?
Is that necessary for all players/servers or only if the player/server is beta? I don’t remember doing that, yet I can see zombine fine. (This thread is for my friend who can’t see it).
Make sure your friend’s client convar “cl_downloadfilter” is set to “all”, it could cause problems if it isn’t.
Currently, only some models/textures will not be visible if you haven’t subscribed to the beta but with GMod moving to SteamPipe in the next update, it will be required.