Was is generally accepted as singular - 'a dog was in the garden', were, plural - 'some dogs were in the garden.
So why is 'You was in the garden' so wrong, (you were in the garden) but have to be 'you were in the garden, singular and plural? It seems to be restricted to only the noun 'you', which could be singular or plural - and in a lot of cases, that fact remains hidden.