have you played through D-Ice's levels before in an earlier game? There's a glitch in the game where if you've finished these levels and start the game over, the Purple Nines will disappear. The only way to get them back is to delete the entire GTA3 file from the PS2 Browser Menu and start the game from scratch.
If you haven't played through this part before, i'm not sure why they won't show up. Have you tried driving around the hideout or have you been looking for them near the phone? I find more of them in the hideout area, just keep circling the block and their vans don't usually start ramming until i'm nearly finished.