Alright, no matter WHAT i try and do Vulpes will not appear in Nipton!
Even tried Ghosts quest to see if that would make him pop up. but noooo!
The lotto winner wont show up either when i first entered nipton!

Anyone know the questid for cold, cold heart? that might help....

FalloutNV.esm
More Perks.esm
FOOK - New Vegas.ESM
Compiled Patch.esp
DarNifiedUINV.esp
NewStripMapMarkers.esp
Arwen_NV_Realism_Core.esp
FOOK - New Vegas.esp
CONELRAD 640-1240.esp
More Perks Update.esp
PerkEveryLevel.esp
Fellout.esp
Jswords4saleDMGPlus5.esp
IncreasedLegion1_1.esp

Total active plugins: 14
Total plugins: 14

Unload all of your extra patches and mods
go into the town
start the quest
save
exit to menu/the game
load your patches and mods
load your save with the quest started/in your quest log

From a very short time looking around at Nexus, this quest in particular is very commonly bugged with any patch that affects the legion, what I posted above seems to be the suggested workaround.

alright, ill try that.
means starting a new game, but i might as well anyways.