Then its obvious, that you do not understand priority. You may cast your creature spell as though it had flash, but you still have to have priority first to do so. And during any step or phase where players get priority, the active player, so your opponent, gets priority first. He also gets priority first after any object on the stack resolved. If you cast your Scouts Warning in the main phase, and it was the only object on the stack, then after it resolved it was your opponent's main phase, the stack was empty, and he had priority. That's sorcery timning right there, and so he was allowed to cast his non-flash creature spell, before you could cast your now flash creature.

Scouts Warning does not let you cast a creature spell during its resolution, not does it steal priority from the player who normally gets it first.

You can flash in your creature before your opponent can play his creature spell, if you cast it during any step or phase that is not a main phase, or there is something else still on the stack after it resolves, thus invalidating the "main phase" or "empty stack" requirements of sorcery timing

LOL 2 @Rezzahan#77802 , im gonna make a draw just for you.

I cast scouts warning on my opp turn to give flash on one of my creatures on hand but then my opponent casts one of their own creatures like it does have flash (before you ask, no, he didnt cast scouts warning and no, his creature doesnt have flash).

+ im adding a full 4k resolution before people calls "Is WhAt ThE cArD sAyS iT dOeS"

Yes, that is what the card says it does. The issue is?