She [topic-は] trip-during lost ring [object-を] found.
旅行中なくした指輪 — a relative clause (旅行中なくした, 'lost during the trip') modifies 指輪 (ゆびわ, 'ring'). なくす ('to lose') is casual; 失くす is another spelling. The sentence packages a before-and-after narrative in one line.