When you view a BIM 360 Gluemodel it is added to your recent models for quick access at any time. If you intend to access recent models when you are offline, then make sure that you have turned on the Keep me signed in option on the Sign In screen.
Local models, which are models that you have added directly to your device via iTunes®, are always available when you are working offline. These are stored on your device and are not synchronized with BIM 360 Glue. It is recommended that you use BIM 360 Glue to ensure that you always have the most up to date models.