"I couldn't find anyone to talk to" = I wanted to have a conversation with someone and I couldn't find anyone.
"I couldn't find anyone to talk" = I needed someone to speak (maybe to give a lecture or to read out a message) but I was unable to find anyone to carry out that task.
In the first sentence, two people would have been speaking if the person writing the sentence had been successful.
In the second sentence, only one person would have been speaking.
- For Teachers