Check the big drawer under the bench seat.
I know someone who left them on the bench seat, then sat on them. They were forced between the seatbelt clips into the drawer below landing on a storage bag.
Of course this lady, being ever so bright, then rummaged around the drawer and in doing so must of enabled the keys to slip into the bag. This daft old bat then decided to strip out all the cupboards and drawers in a frantic effort to find keys and so every bag, box and container was dumped outside the van. She then proceeded to tear apart the inside whilst what she was looking for was outside