The company is not in error for issuing a 1099. He was paid more than $600, and he was not an employee.

Either they paid him a fixed amount or he filed an expense report. The company might have paid per diem for some expenses. If he filed an expense report does he have a copy of it?

A 1099 doesn't report details. Whether or not he kept sufficient receipts to cover the entire amount is a different problem.

If it ran $1,000, then he probably stayed in a hotel for a night. He should have receipts for air fare, food, hotel, rental car/cab/public transportation in San Francisco, transportation to/from SEA airport, and parking at SEA if he left his car at SEA airport.