Learn Turkish: Cüzdanda bilet yok. - There is no ticket in the wallet.

The base word is cüzdan (wallet). To say "in", "on", or "at", we add the locative suffix -da or -de. Because the last vowel in cüzdan is "a", we use -da to follow the rules of vowel harmony.

Why isn't there a word for "the" before wallet or "a" before ticket?

Turkish doesn't have a specific word for "the". Context tells us it means "the wallet". As for "a ticket", you could say bir bilet, but in general negative sentences like this, Turkish often drops bir.

Why does the sentence start with cüzdanda instead of bilet?

In sentences talking about whether something exists or not (using var or yok), the location usually comes first. The standard Turkish order for this is Location (cüzdanda) + Thing (bilet) + doesn't exist (yok).

What exactly does yok mean here?

yok means "there is not" or "does not exist". It is the direct opposite of var (there is / exists). We use it at the end of the sentence to express that the ticket is missing.