I'm so tired of those half-wit people camping limited-supply pattern vendors legitimate mean to make a buck my ass. Been seeing the Moonglade patterns on our AH at 1000% profit for weeks now.
Blizz should remove the limited supply thing, or make limited supply items BoP end of story.
Nighthaven is a town in Moonglade where all the residents are druids of the Cenarion Circle, a faction that starts out neutral to both Horde and Alliance.  At level 10 Druids of both factions receive a spell that ports them to Moonglage as part of their bearform quest.  There are two druid only flightmasters in town who will fly you for free to TB (Horde) or Darn (Ally).  Outside of the town are fligthmasters for Horde and Alliance which anyone can use once they talk to the flightmaster, the Horde one is by the felwood tunnel and the Alliance one is further around the lake.  During the Lunar Festival that occurs once a year you can talk to people in major cities and get ported to Moonglade, anyone can do this and if you do you should get the FP when you are there as well.
The other method of getting to Moonglade is to run through the Felpaw tunnel from Felwood.  You can do this by earning rep until you aren't KoS (level 50ish quest/mob kills) or you can kamakazi through  which will likely turn into a corpse hop if you are below level 50.  Like any other corpse hop, you can bag or bank all your durable gear so deaths don't cost anything.
The Cloak pattern is BoP, but this robe pattern is not.
They should do what they did with instances make these respawn for just each person.  That way its not a limited supply.  Sure someone can put on the AH but then about 100 other people can too.
I don't know about this robe pattern, but for a few of the alch potion recipes, only one per 24 hour period is sold at a specific vendor.  It sounds as if this is the case with this recipe.  Keep tryin folks :)
I sat there for 3 or more hours (I lost track) and the boot pattern spawned ONCE!  Never did see the robe.  And I was doing it in the wee hours so no one stole it out from under me either.  It is a SLOW respawn rate on this pattern.  Same for the other Moonglade vendor (enchanting patterns and felcloth boots).  It's enough to drive you mad.
I kinda understand why they AH for so much.  I'm not going to pay it mind you, but sitting there doing nothing but clicking on the vendor over and over is mind-numbingly difficult work.  Sooooo boooring!
Then again, maybe they just really slow down the respawn rate at night because there is no competition.  I don't know.  Try again tomorrow I guess...
Ever since the new patch, people have been hogging them in moonglade 24 7. I just sat there (reading a book) at like 7am and NOTHING! Even the runecloth belt didn't respawn. Then when I went back to Ironforge, someone in the trade channel said he's selling the pattern for 30g... outrageous!
I just went there and he had the pattern without me waiting a minute.  I bought it and then checked again and he had the pattern for the runecloth cloak.  So he definitely has the pattern.  Maybe I just got lucky.  I have no idea how often it spawns, but it's definitely still there.  I'd try going at an odd time of day if you are worried that someone else might buy it.
take a priest with you and go throght cave. THERE IS A FLIGHT PATH IN MOONGLADE. its like two feet away from the exit of the cave it is only for horde =D hope it helps
It's there. At least when I pulled up (9pm server)- best idea if you are having issues with the respawn rate: Log out next to vendor, and log back in every couple hours, assuming you can play a different toon for a bit.