Learn Finnish: Pöydällä oli ilmoitus, mutta sitä ei luettu. - There was a report on the table, but it was not read.

It is formed by using the negative word ei (no/not) followed by the passive past participle. For a type 1 verb like lukea (to read), the passive past participle ending is -ttu, giving us luettu.

Why does the k from the basic verb lukea disappear in luettu?

Passive forms are built on the weak grade of the verb stem. For lukea, the consonant k disappears in the weak grade, just like it does in the first-person form: minä luen (I read).

Why is the word sitä used instead of the basic form se (it)?

Sitä is the partitive form of se. In Finnish, whenever the object of a sentence receives a negative action (like ei luettu here), that object must always be in the partitive case.

Why doesn't the Finnish sentence have a word for "There" as in "There was a report"?

Finnish doesn't use a filler word like "there" for these types of sentences. Instead, it relies on a "location-first" structure: it starts with the location (Pöydällä), follows with the verb (oli), and ends with the new information (ilmoitus).