Megan Lacy Wren, 25, was last seen at about 3 p.m. March 31 near Vermont Avenue and Wilshire Boulevard in the Westlake area, said police.
In an earlier statement, authorities said Wren's family was very concerned about her unexplained disappearance especially given that she has a serious medical condition and is in need of care. The nature of her health condition was not disclosed.
A celebrity gossip site described her as Sizemore's girlfriend. The two apparently had been living together six months prior to her disappearance.
However, Sizemore's manager Charles Lago described Wren as just a friend.
"She's a girl he's known for a long, long time, but she's not Tom's girlfriend," Lago said. "She used to live in the same building. ... he tried to help her."
Sizemore has cooperated fully with police, and has spoken recently with her father, Lago said.
City News Service contributed to this report.