What happens if the officer didn't read me my Miranda rights?

The belief here is that a missing warning is a defect in the whole case. It isn't. Miranda governs one thing: whether statements obtained through custodial interrogation can be used against you.

If the warnings weren't given when they were required, the remedy is suppression of those statements. Physical evidence, the officer's observations, video, witness testimony, and the arrest itself are generally unaffected.

There's also a threshold question people skip. Miranda applies to custodial interrogation — both parts required. If you weren't in custody, or if nobody questioned you, there was nothing to warn about. Officers are not required to read Miranda at the moment of arrest, and often don't, because they don't intend to question you.

Where it does real work: in cases where the statement was the evidence. A confession, an admission placing you somewhere, an inconsistent account. Losing those can be decisive.