Sean had been on the island since September 9.
He has been friends with David, 24, since they met in Leeds last year.
David was studying at Leeds University and they were friends on Facebook.
But he didn’t even realise he was on Koh Tao until he saw a Facebook posting.
They had arranged to meet on the night of the murders but Sean was hungover and didn’t get out of bed.
Hours after the murders Sean posted: “My mate Dave lost his life on koh Tao. We were meant to meet up when we found out we were both there at the same time
but I fell asleep.
“He was killed that night. I feel f****** terrible.
“I loved you so f****** much brother. I know you tried to save her.
“You are the most honourable guy I’ve ever met. I will miss you terribly.
“I’m sorry I didn’t come out with you that night. Really my heart is breaking.”