''I hit a maul and it did not feel right. I just knew I needed to get it looked at. There was still good strength in my arm. But the specialist looked at it and said it is gone.''
Thorn will not get back on the paddock for four to five months.
For a guy who first played top-level sport in 1994, this is his first major injury.
''This has been a new experience for me. I have been lucky throughout my career, as this is pretty much my first serious injury. I cracked my collar bone when I was in reserve grade about 20 years ago.
''It is an interesting experience. It is not very enjoyable; weird, really, and frustrating for me. So I guess a lot of guys have to go through it.
''Just realising I am not going to get to play Super rugby this year is tough. I've just got to be patient. I always like to push things. But if I try and do too much, then I could damage what has been done.''
Thorn had an operation to reattach the biceps to the bone and is out of plaster now but will still have his arm in a brace for the next few weeks.
Aged 39, the 60-test All Black is not ready to quit playing.
''I will say I will play again. This year is a little bit frustrating. I only got to play four games when I am used to playing 25 to 30 games. I definitely want to play again. I've got to look where.
''A guy from the Bulls did the same injury the week before and he is 27. There are guys every week who get injuries and their season is over. It is just because I happen to have the number 39 beside my name. Does that mean my body is telling me something? I don't know.
''It is a contact sport. I go hard and for once, I got an injury. Is it because I'm old now? Maybe, I don't know.''
Thorn said he had a great off-season and had racked up personal bests in the gym.
He won the Highlanders' bench press competition and was not sore after games.
He had studied a couple of papers with the Australian Strength and Conditioning Association and helped out Highlanders trainer Andrew Beardmore in the gym.
So is that where Thorn sees his future, helping throw some tin?
''Possibly, but I would not mind having some go at coaching. But possibly something away from rugby, I do not know.''
Medical advice was his arm should fully heal.
He could come back to the Highlanders but the issue is yet to be raised by either party.
But when he turns 40 on February 3 next year, it will be into the final act.
''Wherever I play next year, that is it. That is going to be my final season. I'm just having a break now; I'm four months away and letting things heal.
''I will get to a place where I am more comfortable, then I will start to train.''
