Mistake e Mistook: Como utilizar

It's correct to say "I mistook".

Ref. thefreedictionary

Won't mistook usu. take a for after it?

"I mistook his face for his back"

Marcio_Farias said:

Won't mistook usu. take a for after it?

"I mistook his face for his back"

Soon, however, I mistook ability for perfection, and I became a bit cocky. ocregister.com

I had never seen such a big dog, so I mistook the dog for a bear. bbc.co.uk

What I mistook for cynicism, they told me, was merely business as usual. washingtontimes.com

As I see it, the economics profession went astray because economists, as a group, mistook beauty, clad in impressive-looking mathematics, for truth. nytimes.com

The verb "mistake" followed by the preposition "for" becomes a phrasal verb, meaning: 'to think that a person or thing is someone or something else'.

The verb "mistake" means: to not understand something correctly. "Mistook" is not so much used because it's formal, but it's not incorrect.

Examples:

• I'm afraid I mistook the nature of our relationship.
• I mistook your signature and thought the letter was from someone else.

Sim, mas não use como verbo como se fosse intransitivo:

Eu errei. = I made a mistake.
Eu cometi um engano. = I made a mistake.
Eu me confundi. = I made a mistake. / I confused myself.

Forma verbal transitiva:
Eu confundi você com ele. = I mistook you for him.
Eu sempre confundo isto com aquilo. = I always mistake this for that.

As I wrote, it's not much used, but here are examples of its use in the following plays by William Shakespeare:
'A Midsummer Night's Dream'

ROBIN
Believe me, King of Shadows, I mistook.
Did not you tell me I should know the man
By the Athenian garment he had on?
And so far blameless proves my enterprise,
That I have 'nointed an Athenian’s eyes.
And so far am I glad it so did sort,
As this their jangling I esteem a sport.

and 'Two Gentlemen of Verona'

Speed. Madam Silvia! Madam Silvia!
Valentine. How now, sirrah?
Speed. She is not within hearing, sir.
Valentine. Why, sir, who bade you call her?
Speed. Your worship, sir; or else I mistook.