Should I tell my sister her husband is cheating on her?

My sister has been away for work, leaving her husband home alone with their kids. Earlier today, my mom decided to check in on him, since her phone ran out of credit she decided to call him using my new phone which also had a new number that he doesn’t recognize. I also didn't have his number. So when my mom called, he answered without knowing it was her. They spoke briefly, hung up, and that was that.

Later that night, I received a text from a number didn't recognize: “Hey honey… Aren’t you finished?” (In Amharic, the phrasing used a feminine form, implying the text was intended for a woman.) Assuming it was a wrong number I replied, “Wrong number, bro.”

A while later, he texted again: “Honey, I’m still waiting. Are you coming?” Suspecting my friends were trolling me, I decided to play along and said: “Where do you want me to come?”

His next messages took a turn: “OMG, I don’t know what I’m going to do to you…” followed by “Do you want me to come to you lick it?”, I was WTF, is this a stranger with a wrong number or someone I know? So I decided to check the number on Truecaller.

When I checked the number his name popped up. I thinking this can't be. So I checked the number in my call history, it matched the one my mom had dialed earlier. I was shocked and confused. Part of me wanted to confront him, but decided to test how far he would go. I replied, “What else would you do to me?”

Suddenly, his tone changed. He awkwardly backtracked: “You silly… anyways, I’ve deposited the amount you asked for. You stupid… I’ll call you later.” Clearly, he’d realized he was talking to the wrong person and tried to reframe the conversation as a friendly or business exchange.

I didn’t respond, and he never texted again.

Am I tripping? What should I do?