My wife was watching the replay when I got home just now (can't watch it live, but can watch it the next day). I got home right when that happened, what a bizarre moment.
From King5 (Seattle local news):
“It surprised the hell out of me,” Kirby said after the game (h/t Seattle Times). “I thought it was the umpire because I had my hands up and asked for the ball. I thought he threw it. I mean, it was an impressive throw. I’ll give him that.”
The fan appeared to be a teenager who was wearing a Mariners jersey. Video being shared around social media and featured on the national broadcast showed the fan appearing to be escorted out of the game by stadium staff.
Mariners manager Scott Servais told reporters after the game that the young fan caught an Astros foul ball and thought he should throw it back onto the field. Fans of the home team at certain ballparks around the country traditionally will throw back home runs hit by the opposing team occasionally, although the baseballs almost never hit one of the players on the field.
https://www.king5.com/article/sports/mlb/mariners/george-kirby-hit-fan-thrown-ball/281-a0120c2e-3342-4d96-bd11-1cadd66a3649