What's the old saying: Revenge is a dish best served cold! I think Tristan has the the right take on the betrayal. While throwing a raging hissy fit and making a scene may have felt good for a couple of minutes, freezing Peter out and then making a cold call months later was delicious. I imagine Peter's fiancee will be wondering who Tristan is and Peter should be more than just a bit flummoxed.
Since it appears they may be in contact some years later, I wonder if Tristan will make Peter grovel?? Or if time will assuage his hurt?