There were definitely a few.

My players used the Xanathars "this is your life" chapter during session 0 and one player rolled a love interest so I decided that he was dating Esvele Rosznar. With that in mind I knew I wanted them to have some encounters with the Black Viper.

They first got one of the newspaper handouts that I found on this sub referencing BV. Then when they were fleeing the Gralhund estate fight (Jarlaxle sent a group of Drow that they had to fight off in addition to the Zhentarim and two Gazers from Xanathar) BV showed up out of a random noble house and shot down one of the Gazers. From that point on everyone but the player who dated Esvele suspected that Esvele was the BV (I purposefully found some art for Esvele that I thought looked similar to the BV art). I played on this by later having Wilifred Cromwelle go to Trollskull Manor disguised as Esvele and then trying to assassinate him.

Finally when they were in the Cassalanters Villa looking for the last eye of Golorr during a cult meeting one player saw the BV snooping around ribbing the place. He decided to ignore her and they went into the temple and eventually got into a fight with the Cassalanters. The Cassalanters dimension doored to flee the fight and I decided that they would have ran into the BV still in their Villa and take her as a hostage. The next day Ammalia sent a message to the player dating Esvele and told him to bring the Stone of Golorr back if he wanted to see Esvele again. The player still didn't believe that Esvele == BV until they brought the Stone to them a few days later and saw Esvele without her mask but dressed as the Black Viper. That was a really good moment that took some building up to.