Hello. I'll be happy to assist you.
You did the most important step by filing a police report.
As for the defamation, there are two problems with such a suit. First, you have to prove that the untrue statement was communicated to someone other than you. At this point, you don't seem to be able to do that. Second, even if you could prove that, you have to show that the communication somehow caused you some financial loss. Emotional distress isn't enough.
As for the text you received, you could take action there, but the issue is identifying who sent the text. While you may think you know who sent it (and you may be correct), you have to have evidence of that fact.
I just don't see a lawsuit here worth your time and money, but getting the police involved was definitely the right thing to do. If the facts develop more, that may change things, but as it stands right now, I just don't see a realistic lawsuit.
I hope that answers your question. If not, feel free to ask follow up questions. If so, please remember to "rate" my answer before you go. Good luck.