passive or active?

The verb disappear is used in both transitive and intransitive forms.

I was wondering for the following sentences which form is being used?

(a) While I was on vacation, my camera was disappeared from my hotel room.

.....

(b) While I was on vacation, my camera disappeared from my hotel room.

Normally in English disappear is intransitive, and passive can't apply. But that's changed recently. In Spanish, however, the cognate verb can be transitive.

The passive use of disappeared, meaning 'missing', 'stolen', or 'kidnapped by an unfriendly government', is a recent borrowing from American Spanish desaparecido. It's gotten a lot of use from publicity of the policies of repressive governments in Latin America in the 20th century, especially Argentina and Chile.

Short answer: Use "disappear" intransitively by default, and transitively only if you're being sarcastic. Otherwise, if someone stole your camera, say someone stole it.

Generally stylistically, you should prefer using the active voice over the passive voice. Some scientific and technical writing requires the passive voice, but the situation with your camera isn't that.

In your specific case, the transitive use of "disappear" is much more recent, and is generally a sarcastic usage. It sounds like a failed euphemism for theft or some other bad act such as a political kidnapping.

I first heard "disappear" used transitively as part of the reporting around the Falklands War, which is when the "Dirty War" of the Argentine military government gained currency in Anglophone news. Mothers of los desparacidos marched in the Playa de Mayo in Buenos Aires, demanding to know what happened to their children. These protests and defeat in the war led to the downfall of the junta and democratic reforms in Argentina.