。
Unfortunately, he lost his passport.
Literal
Unfortunate thing [to-に] he [topic-は] passport [object-を] ended-up-losing.
不運なことに is a fixed sentence-adverb pattern where ことに wraps a na-adjective into a sentence modifier meaning 'unfortunately.' 無くす is the transitive verb 'to lose an object' — the intransitive pair 無くなる means 'to disappear.'