Could My Phone Have Been Compromised by a Police Officer?

A couple of years ago, I reported a crime to the police and, while waiting, an officer asked to see my phone. I felt uneasy, so I handed it over without explanation. He placed his phone next to mine and started fiddling with both devices. When he returned my phone, he told me to turn it off to save battery. After turning it back on, I noticed my navigation bar was different, an app was missing, another had been added, and unexpected old phone numbers showed up in my contacts.

I initially thought it was just him messing around, but then my phone started flashing black every 27 seconds, and while listening to music, it skipped parts of songs by itself. This flickering only stopped after a system update. I later mentioned the idea of phone cloning to the police, but they dismissed me and pressured me to delete accounts that contained evidence of the crime. Oddly, some accounts remain open even beyond the 30-day deletion period. Just to clarify, I have no criminal record and have never been under suspicion. I eventually bought a new phone but still use my old SIM card with my old accounts. What might be going on with my phone?