回复：I just came back from Vancouver

If you have used your visa you got it in Vancouver( I
mean the immigration officer at border checkpoint has
stamped on it,you have to apply a new visa again,if not,I mean if you enter USA with H4 approval notice &
old I-94,the visa is avaliable now.Check your I-94 ,is
it new or old,then you know.
Did you try to contact the VO or US immigration officer at Vancouver international airport before you leaving Canada?