Sonia Ulrich, Monica Kenyon and Marla Saltzer were enjoying a happy hour at Santa Monica's upscale Fig restaurant on Thursday when Kenyon saw Michael Hsu acting suspicious at a nearby table after the woman he was with had gotten up to leave.
"I could see he had something like concealed in [his] hand. And I kept watching and I saw something fall from his hands into the wine glass," Kenyon said.
"All three of us just went, 'Oh my God.' And we just kind of leaned in and were like, 'Okay, what are we going to do?'" Ulrich recounted.
Ulrich tracked down and confronted Hsu's alleged victim in the restroom, reports CBS News correspondent Mireya Villarreal.
"'My girlfriend saw him put something in your drink.' And she said, 'He's one of my best friends,'" Ulrich said.
The trio notified restaurant staff who they say reviewed surveillance footage and called police.
"All of a sudden they appeared and they told the gentlemen, 'Stand up and come with us.' And he didn't say anything," Saltzer said.
Ulrich posted her friends' story on Facebook, which has since been shared more than 100,000 times.
"I just want to let people know, if you say something, something really good might happen. It might really help someone who needs it," Ulrich said.
After his arrest, Hsu showed no reaction after pleading not guilty at a Los Angeles court hearing on Tuesday. He's charged with administering a drug and assault with intent to commit a sex crime.
"There's no indication that Mr. Hsu, again, based on these allegations, represents any kind of a threat to the public," his defense attorney Alan Jackson said.
Hsu is being held on a $350,000 bail and is due back in court in two weeks. He faces up to six years in prison if convicted. County prosecutors say they're awaiting test results on the woman's drink.
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