According to family members, Jeremy Hansbrough was last seen on Monday, May 16, though the 29-year-old has been spotted by others.
On Thursday, someone reported seeing him near 28th Street and Pico Boulevard in Santa Monica.
Hansbrough reportedly takes medication for seizures and doesn't have the medicine with him at the moment.
His mother, Michelle Hansbrough, has since filed a police report and has put up posters in an effort to bring her son home.
She said he's high functioning, but doesn't communicate with people he doesn't know very well.
"If they see his picture, just call 911 or call the number on the poster so we can find him, because the lapse in time, the time people talk about where they saw him and the time that we can get there," said the mom. "So if they keep him talking about jazz. He's a jazz aficionado."
If the man isn't found by Friday, there will be a search party on Saturday, according to the family.
Anyone with information is urged to contact local authorities.