The family was supposed to return home Sunday, but they remain in San Bernardino searching for Lukacik.
"This is so uncharacteristic of him to be gone like this," said Lukacik's father, Joe. "It's four days now, and it's just not like him at all."
The family had been skiing Thursday and Friday when Lukacik apparently had an accident on the slopes, fell and hit his head, leaving him disoriented throughout the night.
The family said that he didn't know where he was at one point.
It was around 12:30 a.m. Saturday that he abruptly walked out of the cabin in the 1300 block of Balsam Drive, saying he was going to walk home to San Diego.
"Early on, we considered this a voluntary missing because he did have some conversation with his father," said Capt. Greg Garland of the San Bernardino County Sheriff's Department. "As time goes on without any contact with family or friends, the concern has been heightened."
Lukacik was dressed only in a shirt and jeans. He also did not have his cell phone.
His family said he's also bipolar and is without his medication.
Anyone with information is asked to call the SBSD at (909) 387-8313.