"If You Never Answered X": an iPhone has some found footage of a kidnapping (for Dateline?)

Daniel McKee offers a 6-minute short from the UK, “If You Never Answered X”, on the Omeleto channel. 

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A young man’s iPhone is found in the country, and his messages can be traced, including unpaid bills.

He seems to have been last seen at a party. How do you get kidnapped at a party in front of other people?