When opening a Detached drawing, the software checks all sheets in the drawing to be sure that they are synchronized with the model. If not, you are warned.
If a Detached drawing is open, and you open a model document, either from File, Open or by right-clicking a view and selecting Open, the drawing does not synchronize with the model until you load the model.
When you load a model in a detached drawing view, all unsuppressed models in the drawing document are loaded (including models on different sheets), regardless of whether the models are related. This ensures that all models are updated when you make a change.