
The Del Norte County Sheriff's Search and Rescue Team, armed with cadaver dogs, boats and helicopters, had searched the area four times in the last week without finding any sign of the missing woman.
"I'm appealing to this young man," Morris said Wednesday before Dickson's body was found. "We've got a lot of big question marks in his timeline and we're working to nail it down."
Police said Miller has described himself as a friend of Dickson's but denied knowing where she was.
After initially talking to police, he has invoked his right to an attorney. Attempts by ABCNews.com to reach Miller were unsuccessful.
Suspicion of Miller's possible role grew when a police search of his truck found what a preliminary test identified as a protein sample. Investigators are waiting for further test results to come back from a crime lab.
"We've done some chemical tests that indicate there was protein on the seat," Morris said. "We've sent it off to make sure it's blood."
If it is blood, authorities must then determine whether it came from Miller, Dickson or someone else.
Investigators for the Del Norte County Sheriff's Office collected the protein sample after obtaining a search warrant to search Miller's vehicle. The truck, Morris said, had been cleaned and stripped of some of its seating upholstery before the search. The evidence was collected from the foam lining beneath. Authorities also seized Miller's computer and some clothing.
Miller told police that he met Dickson to make the drug buy the night before her burning car was recovered. According to Del Norte County investigators, Miller said that he grew paranoid about having the marijuana in his truck after he left Dickson and pitched it into a river.
Investigators have not yet confirmed reports placing Miller in Crescent City after 10:30 p.m. the night of the exchange.
Dickson's family pleaded Wednesday for any information that might help find the woman.
"My daughter turned 24 on Saturday," Sandra Davis, Dickson's mother, said in an interview with ABCNews.com before her daughter's body was recovered. "What do you say about your child? She was a beautiful woman."