Learn German: Ja, das Fundbüro ist hier. - Yes, the lost and found office is here.

Fundbüro is a compound word made of der Fund (the find) and das Büro (the office). In German, the last word in a compound noun always determines the gender, so it takes the neuter article das.

How would I say 'This is not a lost and found office' using the rules from this lesson?

You would say, 'Das ist kein Fundbüro.' Because Fundbüro is a neuter noun (das), you use the basic form kein to negate it in the subject position (nominative).

What does Fund in Fundbüro literally mean?

Fund translates to a 'find' or 'discovery.' It comes from the verb finden (to find). So a Fundbüro is literally a 'find office'—the place you go when you have lost something and hope someone else has found it!

Why does the verb ist not come right after Ja? I thought the verb had to be in the second position.

Words like Ja (yes) and Nein (no) at the beginning of a sentence are treated as completely separate. They do not count towards the verb position rule. In the main sentence, das Fundbüro takes up position 1, and the verb ist safely takes position 2.