If you can’t find any kids in this post, it’s because they’re true hide-and-seek masters! I’m kidding.
As anyone who has kids knows, children are like ostriches: if they cover their heads, they think they’re invisible. (disclaimer: ostriches don’t actually do this)
Until around 7 years of age, most children are not yet sufficiently cognitively developed to be able to take another individual’s perspective into consideration. Therefore, when they close or block their eyes, not only can they not see anything, but they think that nobody else can see anything either.