Rob Kardashian allegedly went missing last weekend.

The 'Keeping Up with the Kardashians' star's mother Kris Jenner and sister Khloé Kardashian were reportedly terrified and on the verge of filing a missing persons report because they couldn't locate the 28-year-old sock designer, who has been battling depression for some time, for three days.

A source close to the family said: ''Rob had been at Khloe's house Friday morning, and left without telling anyone where he was going. Khloe was out of town but her assistant was at the house. After learning Rob had left, Khloé began calling and texting her brother to check-in. After not hearing from Rob for over 24 hours, she called her mom, Kris. Kris began calling Rob's friends, and dispatched staffers to go by Rob's condo.

''Rob wasn't at his condo, and his friends had no idea where he was.''

While Khloé was eager to call the police, Kris ''didn't think it was necessary.''

The insider explained to gossip website ''She thought Rob would get very angry that the cops were called, and it would have created a media circus. Finally on Monday morning, Rob came back to Khloe's house, not offering any explanations for his whereabouts. His disappearance certainly wasn't a good thing, and Khloé is afraid it will happen again.''

Khloé, 30, recently admitted she is very worried about her brother.