So I had the recipe for Costco's Buttercream, and now I can't find it, I called the local costco and she said that what is in it is Powdered Sugar, Salt, Shortening, B & V and milk powder, what is b&V??? Anyone make a buttercream that is similiar to Costcos?

May be it's butter & vanilla?

Here's one:

COSTCO Mousse recipe

http://cakecentral.com/recipes/7308/costco-mousse-recipe

If the buttercream recipe has ps, shortening, salt and milk powder - it only lacks flavoring/s: butter and vanilla extracts.
(and probably some water to thin it a bit).

HTH