I thought you didn't hear because you were busy doing something else. You're a good listener
直訳的にyou listen wellになりますが、
英語で大体、you're a good listenerやyou're good at listeningと言います。
あなたが他のことをしていて忙しそうだったので聞かれていないと思っていた
I thought you didn't hear because you were busy doing something else.
実は聞かれていた。よく聞いてるねー
but you did. you're a good listener
と言う表現を使えますね。
ご参考になれば幸いです。
**Wow, you were really listening!**
**I didn’t think you were listening, but you caught that!**
「聞いてたんだね!」という驚きの意味を出すには、**you were listening!** や **you caught that!** のようなフレーズを感嘆調で使うと自然です。