The play happened in the sixth inning of Friday's 4-2 Angels win over Houston with the score tied 1-1. An unidentified Astros player sitting on the bench yelled "I got it!" as Conger was preparing to catch a foul pop-up hit by Houston's Chris Carter.
Conger, believing teammate Mark Trumbo had yelled, let the ball drop. He was charged with an error, which was later changed to "no play."
Porter issued an apology to Angels counterpart Mike Scioscia over the incident, the Los Angeles Times reported.
"I apologized to him on behalf of our ball club," Porter told reporters. "It's not something that I condone, and I take full responsibility. It won't happen again."
"I think we've moved on, regardless, but that's a classy move," Trumbo said. "It's a strange thing, but it was nice of him to extend the apology."
There was no word on which Astros player distracted Conger.