It was when Geralt speaks to Foltest:That last quote is nonexistent I believe. Geralt said in TW1 that he has a feeling that Triss is important, so people say that he confused Triss for Yennefer.
"Foltest and I talked about the women in my life and I realized I have feelings for Triss. My amnesia prevents me from remembering our relations in the past, but I have the impression I once loved a sorceress, deeply... Triss suggested how I might regain my memory, and I think that at heart she wants me to realize she was the love of my life. I realize now that Triss is the love of my life."