Remove a water stain?

[godofmustard.livejournal.com]

A while ago a small amount of water dripped onto my IW Marie Rose and it stained it, but I've been uncertain for how to clean that. I've looked up removing water stains and also some care for IW products but there are so many different suggestions that I don't know which one to go with! The fabric is listed as polyester, but for that I saw many methods involving actually wetting the product... needless to say I'm uneasy about doing that considering what two drops of water did... Does anyone have knowledge of what's best for this item in particular? Thanks!