The Gov can acquire data that you - with full willful consent - have chosen to make publicly available. eg: public social media posts.

Can the government use my ex-wife's autobiography detailing the crimes she saw me commit in order to help investigate me?

Because search is the scope of our discussion, the answer is that the government can read your wife's book for the same reasons they can read your book.

Is one suggesting not detailing our crimes in any recorded format and making it public if we do not want said recordings to be part of a government investigation?