After studying my peace lily closely, I see it has one, but occasionally two, leaves per stalk and these leaves form at the end of the stalk, not part way down. I would say the one you saw may be misnamed.
The scarlet leaf is possibly a form of Ludwigia. It is green on the top of the leaf and red underneath. Can't say it looks like silver beet though.
A plant sometimes seen is cherry leaf, sometimes called temple leaf, Hygrophila corymbosa syn. Nomaphila stricta.
Another possibility may be Barclaya longifolia. Though the red form has red upper leaves. Can you post a pic? There are a number of red plants available now.
Most red plants require a lot of light to keep their redness.