In recounting the events on Facebook, Ms. Ulrich said she and her companion, Ms. Kenyon, had gone with Ms. Saltzer to the restaurant at the Fairmont Hotel for happy hour. At one point, Ms. Ulrich noticed Ms. Kenyon “making a funny face.”

What had caught her attention? A man nearby had just slipped something into his companion’s drink, Ms. Ulrich wrote:

“He pulled her glass toward him, kind of awkwardly, then he took out a little black vial. He opened it up and dropped something in. Then he tried to play it cool, like checking his phone and hiding the vial in his hand and then trying to bring it back down slyly.”

Ms. Ulrich continued: “Now, Fig is a nice restaurant. We were enjoying our charcuterie platter and some fancy cheeses. That type of place.”

She wrote that the couple “had a bottle of wine they were splitting.”

“It seemed like a first or second or third date,” she said.

The man’s dinner companion had gone to the restroom.

“After a few ‘Oh God. What do we do’s,’ I got up to find her in the bathroom to tell her. Warn her. Tell her to get up and leave this creep. Make him drink it. Something,” Ms. Ulrich wrote.

She awkwardly loitered by the sinks in the bathroom, waiting to speak to the woman. “I approached: ‘Hey! Um, this is kind of weird, but, uh, we saw the guy you were with put something in your drink.’ ”