Ms Figard, 19, disappeared after accepting a lift from a lorry driver at the Granada services on the A34 at Chieveley in Berkshire.
The driver who picked up Ms Figard, an accountancy student, could have offered to take her to Salisbury. From there she intended to get a bus to Fordingbridge, Hampshire, to spend Christmas with her cousin.
Her father, Bernard, said: "Celine, if you can hear us, if you can see us, please show yourself. Your family and friends are waiting."
Mr Figard, 44, a farmer from the village of Ferrieres-Les-Scey, 220 miles south-east of Paris, said his daughter was a "timid but very happy person" who was serious about her school work. He appealed for any information that might help the police to find her. He said: "Please keep helping us. We need to find Celine."
Detective Superintendent Des Thomas, who is leading the inquiry which has been upgraded into a murder investigation, said: "We all hope and pray we will find Celine alive - it will be the best thing that could happen - but experience has shown that is not necessarily the case after this amount of time. I wish it were otherwise. "I have no doubt at all we will find this lorry driver. My great concern is we will not find him in time to recover Celine."
More than 100 officers are now involved in the investigation. Police spent yesterday searching roads between Newbury and Salisbury, but apparently found no trace of Ms Figard.
Detectives are also examining video footage from surveillance cameras at the service station where she disappeared. The search will resume at first light today
Police also issued posters featuring a picture of Ms Figard and an artist's impression of the lorry driver. The driver is described as well-built, ginger-haired, and has a distinctive chinstrap-style beard with no moustache.
He was driving a white Mercedes truck which was towing a light grey 38- 40 tonne refrigerated box trailer. Ms Figard is slightly built, 5ft tall, with brown wavy shoulder-length hair and brown eyes.