It is a common misperception, helped by many TV shows and movies, that police are always required to read you your rights when you are arrested. That is not the case. They only have to read your rights if you are in custody, meaning not free to go, and they are asking you questions. If the police fail to read you your rights, you are in custody, and, they ask you questions, they cannot use any information that they get from your answers against you. Even if the police read you your rights, if you still talk to them, they can use what you say against them. If you are not in custody, meaning an officer calls you, knocks on your door, or comes up to you on the street and asks you questions they can use your answers against you even if they do not read you your rights.
If the police do not read you your rights when they should have that does not mean that the case against you is dismissed, it just means they cannot use the statements that they got against you.
What does all of this mean? If the police are talking to you about a crime, it is serious business, you need to take it seriously, and get good advice before you think about saying anything.
Ed