Why did the traffic police find the ex-wife's phone number when her ex-husband hit someone?

In order to investigate a case, the police have the right to retrieve the contents of mobile phone messages and calls, that is, to take technical investigation measures, but they are strictly restricted.

according to the law, it must be strictly implemented in accordance with the types of permitted measures, applicable lovers and time limits. Investigators shall keep confidential the state secrets, business secrets and personal privacy they have learned in the course of taking technical investigation measures. Procedures unrelated to the case obtained by technical investigation measures must be destroyed in time. Procedures obtained by technical investigation measures can only be used for investigation, litigation and trial of crimes, and shall not be used for other purposes. The public security organ shall take technical investigation measures according to law, and the relevant units and individuals shall cooperate and keep the relevant information confidential.