I haven't had this happen to me yet, but it is one of my biggest concerns given how accessible plates are.

I would start with PennDOT and see what they say.

If you get them to issue you new plates and cancel the old ones you should be good. I haven't read the full statutes in a long time (and I'm not a lawyer), but PA makes it illegal for you to be responsible for tickets from a stolen plate. As long as you have an affidavit for such. I believe that is issued by PennDOT.

The police report isn't enough on its own is my understanding.

https://law.justia.com/codes/pennsylvania/2010/title-75/chapter-13/1333/

https://www.dot.state.pa.us/Public/DVSPubsForms/BMV/BMV%20Forms/mv-44.pdf