Learn Spanish (Latin America): Fue mi grapadora la que desapareció ayer. - It was my stapler that disappeared yesterday.

In this type of cleft sentence, we are singling out a specific item. Using la que (which matches the feminine singular grapadora) translates more closely to "the one that". While you can sometimes use just que in cleft sentences, using el que / la que / los que / las que adds stronger emphasis and is very natural when identifying the specific subject that performed the action.

Why are both fue and desapareció in the preterite tense?

In cleft sentences, the tense of the verb ser (here, fue) generally matches the tense of the main verb (desapareció). Because the stapler disappeared at a specific, completed time in the past (ayer), the preterite is used for both. If you were talking about a present habit ("It is my stapler that always disappears"), you would use the present tense for both: Es mi grapadora la que desaparece siempre.

Could I change the word order to put the emphasized part at the end?

Yes, you can invert the sentence to say La que desapareció ayer fue mi grapadora. This translates to "The one that disappeared yesterday was my stapler." Both structures are very common in spoken Spanish and do exactly the same job: putting a spotlight on the stapler.

Wait, isn't "desaparecer" a reflexive verb? Why isn't it se desapareció?