He does not appear on the scene during the stabbing... I don't know when else he'd appear.
Anyway, I think I can explain the reason why the other party members chose not to join Serge (as Lynx) is because Lynx maybe a character to fear or dislike. Consider what he has done to El Nido. Lynx keeps on talking about enmity (hostility) between Serge and the world. This may have been a part of the enmity he was talking about: rejection and hostility from Serge's very own allies. He was also talking about his and Serge's reversal of roles. Like, Serge'll have to be Lynx for now.
Remember what Marge (Serge's mom) said: (inaccurate) There are people who will not judge you by your looks. Keep your head up.
I think it was merely because they judged Serge by his looks, even if he claims to be Serge, not Lynx.
