ORLANDO, Fla. -- An appeals court has denied a motion to lower the bond for the mother of a missing 3-year-old Orlando girl.

The 5th District Court of Appeal in Daytona Beach on Monday denied Casey Anthony's motion for a rehearing. The motion was sealed.

Anthony is being held on $500,000 bond on charges of child neglect, making false statements and obstructing an investigation. Police said she lied to them and didn't report her daughter, Caylee, missing for more than a month.

A message left with a spokeswoman for Casey Anthony's attorney was not immediately returned Monday afternoon.

Detectives and family members had hoped Caylee would be home by Saturday, the girl's third birthday. She was reported missing July 15.

Grandparents Visit Detectives

The grandparents of Caylee Anthony met with detectives on Monday for about two hours in a nonscheduled visit.

George and Cindy Anthony were at the Orange County Sheriff's Office from about 9:30 a.m. until 11:30 a.m. in what they called an exchange of ideas.

Cindy Anthony said she talked with detectives about a phone call that Casey Anthony said she received in which she heard Caylee in the background. According to a search warrant, detectives said phone records show that the phone call never occurred.

"We discussed that with the deputies today. They're re-looking at the phone records because that's a misstatement," Cindy Anthony said.

Mobile Billboard

Also on Monday, George and Cindy Anthony were pulling a mobile billboard behind their vehicle showing information about Caylee.

"This is a very important day for me to be doing this," George Anthony said. "I'm not letting negativity come into play because negativity comes in and that's all people go on."

George Anthony said he did not know exactly where they would be driving.

"A 3-year-old girl's missing. I think people should look at that and say, 'My gosh, what can I do to help find her?'"

Lee Anthony, Casey Anthony's brother, is scheduled to visit her on Tuesday, and her parents are set to visit her on Thursday, although it is not known if Casey will allow the meetings. She has canceled the last two visits with her family.

Psychic-Led 'Blind Driving'

Meanwhile, a psychic detective and her team are "blind driving" around Central Florida searching for Caylee Anthony.

"We will not even look at street names," psychic detective Gale St. John said. "We drive and go completely on feeling instinct, chasing down what we call a person signature."

St. John and her team arrived in Central Florida and immediately began using specially trained cadaver dogs to check areas on foot over the weekend near Lee Vista Road.

St. John, who is part of a group that calls themselves the "Body Hunters," has been on "Larry King Live," Court TV and the Discovery Channel after helping authorities recover missing children and finding at least one body.

She said she has not received a feeling on Caylee's location but claims it is still early in her searching process.

The team will be driving around the region on Monday. Another psychic will be helping in the search as well, Local 6 reported.

Air Tested

Local 6 has learned that a lab affiliated with the University of Tennessee may be using a new type of technology to test air samples taken from the car of Caylee's mother, Casey Anthony.

Cadaver dogs led detectives to believe there were signs of decomposition in the trunk of Casey Anthony's vehicle and hit on two spots in the child's grandparents home early in the search for the missing girl.

The lab apparently testing the air samples, called The Body Farm, is run by the school's anthropology department.

A researcher at The Body Farm has developed an artificial nose of sorts that can sniff out evidence of human decomposition and decay.

It works by recognizing compounds found in the air where decomposition occurs.

Detectives won't confirm where the samples were transported to, but they said the air samples are being tested for decomposition.

Another Visit Rejected

Also over the weekend, Casey Anthony turned down another Orange County jail visit from her parents.

Casey Anthony's mother, Cindy, said she was not sure why Casey canceled a visit.

"I'd like to see her but if she doesn't want to see us, that is her prerogative," Cindy Anthony said. "I'm sure she had her reasons. You always want to see your child but then again, I'm sure she had her reasons."

A national search for Caylee continues.

Watch Local 6 News for more on this developing story.