Suppose that I cast leomund's secret chest and then bind the chest itself with drawmij's instant summons. I'll then send it into the Ethereal Plane, and while it's hidden, I'll end the spell effect.
Leomund's secret chest says that this will cause the chest to be irretrievably lost.
Finally, the question is, if I crush the sapphire after all of this, will I be able to get the chest back? Drawmij's instant summons says the item appears in my hand regardless of physical or planar distances.