If everyone's board disappears all of a sudden, it may be a little groan-inducing, but it's nothing most players can't recover from with a little time
You cast it, look at three cards, decide in what order you want to draw them, or even decide to put them on the bottom of your library if you don't want to draw any of them
In most cases (see below), if you wait until the combatdamage step or end of combat step, it will be after combat damage has been dealt, so the Ninja won't deal combat damage
The same is true if another object has an ability that triggers when a creature with certain characteristics attacks and Identity Thief doesnt have those characteristics until after it becomes a copy
Mega Gardevoir ex Holo Rare, 187/132 Here it is, the aforementioned Mega Gardevoir ex, here in its Holo Rare form
Post about your card on r/PokemonMisprints or the Gotta Misprint 'Em All Facebook Group, too, as many users help value other peoples cards