Usually this trope shows up when a main character believes they are talking to themselves but in reality they are talking out loud. The person they just happen to talk about is right beside them to.
EX:
"Omg I can't believe Tommy is so hot. How is he single?" I said to myself.
"Well my last girlfriend moved away so we broke up because of long distance." Tommy responded as if he could hear my thoughts.
Wait Tommy heard me???!!!!
Something dumb like that. I'm like who experiences this. Like I would believe mumbles or whispered. But if the author clearly says you said it in your head then "Tommy" shouldn't have been able to hear you. 🤷♀️