When working in the sketch environment, there is a "project curve" command, these curves will be created as sketch curves and live in the sketch. There is also a "project curve" command that you can use outside of the sketch; these curves can be created as associative/unassociative and will not be part of a sketch (the associative option will create a project curve feature in your model tree). Perhaps you have one or more of the non-sketch "project curve" features in your model?
Cowski, thats was also what i was thinking about.
some people use the feature projected curves when they don't need the curves for a sketch or get
non-associative curves to extrude a solid from.
It's also possible to use booth methods trough each other.
only when you need the projected curves in a sketch then i preferred to use the projected curve command in the sketcher.