Look For Trouble w/ Undead + Magic Lamp

[bro]

Hello, thanks to all community for this forum and all existing questions and answers :)

Here is a situation that I need help with.
We are playing the game for the third time, and six players are in the play.

I (LVL 5 and 0 bonuses) kick open the door, and it's not a monster. While I was looking at my hand, my friend went to the toilet. I say we will wait for him because I want to look for trouble.

He comes back, and this happens:

I said we wait for him because I would play a monster. Then I drop the "Wight Brothers" (LVL 16/Undead -> 2lvls + 4 Treasures) and say "After this monster, I'm gonna play this:" and put the Magic Lamp on the table that says: "Only on your turn/Single monster vanish/If it was the only monster you may take treasure but don't gain level."

So in my head, this was a logical move because I played the monster stronger than me, and there was no point in asking "Can I fight this monster" because I obviously can't fight him.

That friend starts arguing about how this is not valid play, because they had no time to play with their cars and that this is a timing question of who plays faster. He uses a Mate, for example, because Lamp makes a single monster vanish. I say that timing is the story of all fights because it matters who drops the curse/enragement or any UOO card first. And in this specific case, they could play other Undead on my monster. And I suppose that this is ok until I play them separately.

I need some explanation about this situation :)
2) Is there any exact time to wait after playing the monster we cannot fight?
2) Is this a correct move?