Originally Posted by
safigan
By chance do you have receipts from checked bags?
You can check a bag and still no show the flight. The bag is supposed to be removed for international (but not domestic) as there's a security concern that the person could have deliberately missed the flight.
Other indirect evidence that at least helps to establish that OP was at the airport would be a receipt from an airport purchase, a rental car receipt, a receipt for airport transportation (at either end), etc.
If OP entered a SkyClub, DL should have that data.