Guild Wars 2

From what I can tell, in the past if weapon skins are released via black lion tickets, they are not removed from the game.

I have checked within the vault and the merchant next to the trading post at least 10 times just to be sure in the past few weeks and the Chaos weapons are not there.

Any idea where they might have gone?

Weapons are removed from the game from BLTC vendors. They cycle through, and come back at different times.

http://wiki.guildwars2.com/wiki/Black_Lion_Weapons_Specialist#Notes

Skin sets are regularly removed from the vendor to open up space for new sets, but may return in the future. Lauren Kamieniecki hinted there might be some improvements to these vendors so that skins are always available.

Though, you may find Chaos skins at the (Historical) BLWS in the future, again. http://wiki.guildwars2.com/wiki/Black_Lion_Weapons_Specialist_%28The_Vaults%29

Good luck.