Within the last day or two, a Costa Rican man has told authorities there that he's twice seen a dirty, bearded David Gimelfarb.
Gimelfarb is the Chicago doctoral student who went missing in the Costa Rican jungle almost a month and a half ago.
That park is where Gimelfarb set off on a solo trip last month.
If the man who was seen is Gimelfarb, his strange behavior could be "due to head trauma, infection or poor blood chemistry due to inadequate nutrition and dehydration," Shaw wrote in a post to the "Help Find David Gimelfarb" group on Facebook.
The Costa Rican man looked at a photo of Gimelfarb and identified him as the man he'd seen near the park. He apparently told authorities that the man he saw wasn't wearing his glasses, which Shaw said wouldn't be at all unusual.
The local Costa Rican police are taking the sighting seriously, Shaw said, but they need help. The local police dogs aren't trained to track a specific person and are only able to track scents for a few hours.
They need trained bloodhounds, which can track a specific individual for a great period of time, but there are non in the country.
Shaw said the FBI has trained bloodhounds, but so far searchers haven't been able to secure their help.