He was also the only one who had a viable replacement already training with the squad. Did GH's behaviour give the coach an excuse to revise his selection based on what he saw in training?

Playing for your country should be the highest honour bestowed upon a player. Any individual who thinks that its excusable to miss any form of training/session that they are expected to attend simply doesn't deserve to be included, regardless of form. There are a dozen other players would jump at the opportunity.

Quite possible. Often sick records are used in work to get rid of the ones you don't want, were as those who are good salts get a bit more time.