West Shroud didn't go poof literally though. It's still there, in fact, you can see it looking west from Central Shroud (near spriggan camp) or looking south from North Shroud (where the golems are). In fact we "travel" through west shroud when going the Central->North road (even though there is a zone line, if you expand the in-game map you can see the true distance traveled).

Basically West Shroud was utterly destroyed by the shard of Dalamud that resides at the southern edge of the North Shroud. If you look westward at night you can see the giant aether crystals glowing yellow in the distance. You will also notice that all trees have been razed (damage leaked into Central and North) so we can assume the whole zone is a burnt, barren, rocky wasteland that can't support life. Hopefully one day we can formally step foot in it and not zone through it (same to the rest of the Coerthan Highlands and Lowlands)