Here's why:
* Passive Voice: The sentence is in the passive voice, meaning the action (being stolen) is focused on the object (the wallet) rather than the actor (the thief).
* "Got" is informal: While "got stolen" is commonly used in informal speech, it's not grammatically correct in formal writing or situations.
Here's a breakdown of the sentence structure:
* "My wallet" is the subject of the sentence.
* "was stolen" is the passive voice verb, indicating that the wallet is the receiver of the action.
Alternatives you could use:
* "Someone stole my wallet." (Active voice)
* "My wallet was taken." (More formal)