What is a word for not seeing obvious "warning signs"?

I'm reading a book right now where there are a lot of strange events that the main character doesn't question and I'm having difficulty describing them. What is a word for not seeing obvious warning signs?

For example, in the book, the main character has just gotten a new job and their employer requires them to provide a copy of their birth certificate. The main character does this without questioning it at all. They are not ignoring that this is strange, rather they don't even acknowledge it as strange.

"Oblivious" used to refer to forgetting, but is now often used for this sort of failure to notice. It lacks any special connection to warning signs, as do my other suggestions.

Oblivious

1. lacking remembrance, memory, or mindful attention

2. lacking active conscious knowledge or awareness —usually used with of or to

"Father was oblivious to the man's speculative notice of his wife."

And one I happened across and liked: "In my career I have never felt that my being a woman was an obstacle or an advantage. I guess I've been oblivious." -- Carole King

It seems to me that other close words, more casual and apparently less specific, include clueless and dense.

Again from Merriam-Webster website: Definition of clueless include "completely or hopelessly bewildered, unaware, ignorant, or foolish."

And as to dense, Merriam-Webster defines it as "slow to understand," making it the loosest fit for the word sought. But it seems to me that the word is used as I suggest, for a failure to see what is obviously in front of you.

But I did not find instances of careful writers using the words the words clueless or dense as I have suggested.

If the person is oblivious to these signs because they are focused on something else, you could say that they have "tunnel vision".

This alludes to the visual effect when traveling through a tunnel. You can only see the end of the tunnel, and everything else around you is obscured.

In your specific example, they are probably too focused on pleasing their new boss by following his instructions to think about whether they should follow the instructions.

From M-W

a tendency to think only about one thing and to ignore everything else

single-minded concentration on one objective

From Dictionary.com

narrowness of viewpoint resulting from concentration on a single idea, opinion, etc, to the exclusion of others

Blinkered, similar to tunnel vision from @DCShannon's answer, e.g.:

a blinkered attitude

Definition:

limited in scope or understanding : narrow-minded

Source: merriam-webster

can't see the wood for the trees (uk).
can't see the forest for the trees (us).
​ to be unable to understand a situation clearly because you are too involved in it - http://dictionary.cambridge.org/dictionary/english/can-t-see-the-wood-for-the-trees

Edit: Oops, I didn't notice the single word request tag when answering.

Oblivious:

1 : lacking remembrance, memory, or mindful attention

2 : lacking active conscious knowledge or awareness —usually used with of or to (MW)

The word has a sort of "poetic resonance" (I know there's another term but it isn't coming to me), since it sounds like the antonym of "obvious". And it's frequently used in a sense meaning, roughly, "conscious ignorance" or "intentional ignorance".