I once asked Reb C.D.Katz Satmer BP dyen about buying coffee on NJ17 in the summer when driving up and back from country.
He said if you see a open bottle Chulev Yisroel and there is NO other bottle in the fridge you can NOT use this milk as Chulev Yisroel because if the GOY ran out of CY milk he is nechshed that he switched Non CY for CY, but if you see plenty other closed bottles there is no need to be choyshed.
I believe the same applies here if you walk into a goyishe Starbucks and he has NO CY what stops him from buying chulev stam and pouring it into a CY bottle.
So I believe this is a Shalleh that needs a psak from some poskim in our days.