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を待ってたのに

was waiting for … but

→ を
phrase Rare #43,444
was waiting for … but The object comes before を. The subject is usually understood from context; のに adds a sense of contrast or disappointment.
JA: 友達を待ってたのに、誰も来なかった。
EN: I was waiting for my friend, but nobody came.

トムとメアリーを待ってたのに、あの二人来なかったんだ。

I was waiting for Tom and Mary, but they never showed up.

僕たちトムを待ってたのに、トム来なかったんだ。

We were waiting for Tom, but he never showed up.

私は家も掃除して、ご馳走も作って二人を待ってたのに声もかけてくれないなんて

I even cleaned the house and prepared a feast, waiting for you two, and you didn’t even say hello to me.

— 箪笥＜たんす＞ (2003)

私達さ、トムを待ってたのに来なかったのよ。

We were waiting for Tom, but he never showed up.