The Four Noble Truths are about suffering, not boxes.
So let's talk about loved ones. When a parent loses or misplaces a loved one, sorrow arises. Was the sorrow inside the loved one? The sorrow was not there before, so where did the sorrow come from? Trapped in suffering, what is the escape?
DN34:1.4.27: Renunciation is the escape from sensual pleasures. The formless is the escape from form. Cessation is the escape from whatever is created, conditioned, and dependently originated.
Looking for the end of suffering, we may become dissatisfied with form and eventually explore the formless, perceiving nothingness and emptiness:
MN121:8.7: There is only this that is not emptiness, namely the oneness dependent on the perception of the dimension of nothingness.’
MN121:8.8: And so they regard it as empty of what is not there, but as to what remains they understand that it is present.
MN121:8.9: That’s how emptiness is born in them—genuine, undistorted, and pure.
The truth to be found in boxes does not end sorrow, so we have to look beyond boxes to find the root of suffering. Going beyond boxes we might find a certain emptiness:
MN121:13.4: So, Ānanda, you should train like this: ‘We will enter and remain in the pure, ultimate, supreme emptiness.’
MN121:13.5: That’s how you should train.”
MN121:13.6: That is what the Buddha said.
MN121:13.7: Satisfied, Venerable Ānanda was happy with what the Buddha said.