Maybe they were wondering if Bubba was setting up a drug deal, or arranging to launder terrorist money. Better question is "Why do the Police have my phone?"
I represent Employers, but I can recommend Worker Attorneys in So Cal if you ask.Ask a similar question
The answer probably depends on why the police had your phone.
If the police had my phone and were using it for messaging, I would probably not be talking about it on a public website forum like this one, but might do things like contact a criminal defense attorney or terminate my phone service, get a new phone and number, notify all my contacts that I had a new number and that any communication from my old number is not from me.