The Andorran club???s coach Xavi Roura was unhappy with the way the new Upton Park manager approached the game, which resulted in a 3-0 home win in east London.
Instead of taking charge of the team for the first time, he left academy director Terry Westley in control and only flew in to watch the game from a training camp in Ireland.
Bilic, who was presented to fans before the game, was described by Roura as thinking he was the ???Special One??? after he failed to take a place on the bench and watched from the stand instead.
The Lusitans manager said he hoped Bilic would take a more active role in the second leg next week but Westley said that was unlikely.
Bilic has explained the reasoning behind his actions, insisting taking the reins would have shown disrespect to Westley given he has overseen the early part of pre-season training.
With the Croatian looking after West Ham???s most of senior players and Westley taking a squad largely made up of youngsters into the game, it was a logical call according to the 46-year-old.
Bilic said: “I was thinking about the best way to manage the game and the training camp we have in Ireland.
“I didn’t want to disrespect anyone and especially not a football team from Andorra as I respect them big time.
“I respect Terry and I respect West Ham so I wanted to show respect to Terry as he coached this team and he took them for pre-season in Ireland and knew them all well.
“I didn’t want to be disrespectful to him. Also the majority of the first team is in Ireland so that was behind our decision to do it like this.
“To be honest I don’t really like this kind of situation with one half of the team in Ireland and one half in England.
“But it will be that way until after we play our second leg in Andorra next week. I will now go back to Ireland on Friday to meet back up with the first-team group.”