I just ran into this myself. Either the bow would show up, but the left-hand pistol would be invisible; or the pistols would both show and the bow be invisible. Which it was seemed to be either random or *maybe* determined by your first draw after logging in, but once it decided which to make invisible zoning wouldn't change it. Going to the costume creator would cause it to reset, in the sense it would choose a new one to be invisible.
Trick Arrow/Dual Pistol Defenders don't seem to have this issue.