I saw once the similar situation with bots in demo, but during recording exactly the bots were invisible for me (I was a spectator). I guess You can see bots during recording, but after - when You try to play this demo - bots are invisible, isn't?
How do You prepare the demo? From console by record command or from some metamod plugin like ClanMod or AMX or something? And what version of CS (1.5 or 1.6)?
For recording demo last time I was using ClanMod 1.82b1, but I'm waiting for some good plugin for AMX for recording demo in the same system like do this ClanMod. These demos prepared by me with this latest CM were OK (sPlOrYgOn can confirm this
).