This has been reported before and apparently FIXED. Well on Maj'Dul server this is not the case at all. Can not complete the Side Salad step of the craft quest until I can obtain the vinegar.
I'm looking into this now. She is selling it on our internal servers, she is selling it on Test, but the fix didn't make it to the live servers. It is now scheduled for the next patch.
Didn't make it since nothing appears to have been patched Tuesday, Mum. This was a reset only week it seems.
I just started another thread on this for Skyfire server. Thanks, Denmum! Will the fix go to all the servers?