You are making assumptions here. According to this article the pilots reported the smoke trail was about a mile below them (they were at 7500ft) and the recording of the ATC transmissions proves the pilot said the smoke trail was halfway between him and the coastline. You've made the assumption that the smoke trail was near them at 7500 ft. That clearly is not an accurate assumption.
Actually, I am not making the assumptions here... the radio news report I heard contemporaneous with the event described as being at the same altitude and passing the plane. Bad reporting? Probably.