How to say A was misidentified as B?
AがBと誤認されました or AをBと誤認されました?
Both are grammatical, but have different usages.
"AがBと誤認されました" is a simple direct passive statement:
息子が万引き犯と誤認されました。
My son was misidentified as a shoplifter.
"AをBと誤認されました" is an indirect passive sentence; i.e., someone else (usually the speaker) was (usually negatively) affected by this wrong identification.
(私は)息子を万引き犯と誤認されました。
My son was misidentified as a shoplifter (and I was bothered).
In this example, failing to use indirect passive may sound like you're a little indifferent about your son's trouble.