For anyone who's read my last thread, I did speak to him properly and was very clear. He was still adament there's no affair and everything has been completely fine
For some reason today I checked his phone and found a couple of messages from her (woman he works with). Nothing sexual or whatever but she mentions an old Facebook page he had for his music 5/6 years ago and he talks about one of the songs and she said she likes listening to him
Taking away my obvious not liking any communication, does that sound like flirting? Or that it could be? I haven't brought myself to tell my friend in real life yet