Perhaps you could describe the world in this story you are reading? Does it have an atmosphere which could be close to living in liquid? If so, then presumably the character needed some kind of oxygen [or similar] mask, but has left it in the cupboard where it is floating around.
It could also just mean that the mask is somewhere in the cupboard but he does not know exactly where.
In this story there is a big Continent and a number of islands made of wood. Sometimes, these islands drift in the ocean. This man, Jopale, lives on one of those islands. The atmosphere is not close to liquid. One day a disaster happend, a powerful eruption of gases. Jopale survived the disaster because he wasn't at home. This is how the author puts it:
Suffocation was the standard death, for people and everything else.
The entire valley was killed within minutes. But the high ridges trapped the poisons, keeping the carnage contained. Even before Jopale heard the news, the disaster was finished. By the time he rode home again, crews of mockmen dressed in diving suits had capped the gaeser. Engineers were busy drawning up plans for permanent repairs. And it was safe enough that a grieving survivor could walk to the ridge above, holding a perfumed rag against his face as he stared down at the fate of the world.
