There's nothing in your code that would save or restore a position.
The simplest method would be to let the game handle it:
Code:
anchor:RegisterForDrag("LeftButton")
anchor:SetMovable(true)
anchor:SetUserPlaced(true)
anchor:SetScript("OnDragStart", anchor.StartMoving)
anchor:SetScript("OnDragStop", anchor.StopMovingOrSizing)
Or, if you want to do it yourself, then you need to save the position into your saved variables table in your OnDragStop script, and restore it when your addon loads.