Here are 3 ways to do this:
1. The Edit Contents/Edit Clipping Path buttons in the Control bar. Clicking the Edit Content button (or choosing Object > Clipping Mask > Edit Contents) selects all the masked contents. You can then double-click on any of the objects to edit them in Isolation mode
2. The Lasso tool. Dragging around masked objects with the Lasso tool selects them, even when they fall outside the mask boundary.
3. The Layers panel. Twirling open the group containing the clipping path in the Layers panel will let you access each masked object. Click the round circle to the right of any object to select it.