threw a wrench in

"I like the piano."
Predictably, I was unable to think of a single pianist.
"What about you?" Mitsutsuka asked. "Do you like music?"
"I don't really listen to music. I never have."
"I see."
As this had thrown a wrench in our conversation, I squeezed the handle of my cup with enough force to turn my thumbnail white and brought the coffee to my lips, glanced down for a moment, then took another sip.

"thrown a wrench in" の意味は文脈からすると会話に水を差して、会話が続かない状態にしている様です。慣用句の様なので、辞書で確認します。
この表現は次の幾つかの変形がありました。
threw a wrench into the works, put a wrench in (to) something/the works, throw/hurl/toss a monkey wrench into wrenchがspannerに代わっていることもありました。

・Merriam-Webster: to damage or change (something) in a way that ruins it or prevents it from working properly: We were going to renew our lease, but the landlord threw a wrench into the works by increasing the rent.
・Farlex Dictionary of Idioms: To disrupt, foil, or cause problems to a plan, activity, or project.: We had everything in line for the party, but having the caterer cancel on us at the last minute really threw a wrench in the works!
・McGraw-Hill Dictionary of American Idioms and Phrasal Verbs: to cause problems for someone's plans.: I don't want to throw a monkey wrench in the works, but have you checked your plans with a lawyer?