Hi,
If you got a PCN ticket on your windscreen and lost it. Just wait for a PCN letter to come through, assuming you are the owner of the vehicle and it is registered at your current address.
Alternatively you can email the council of the borough you were in and ask if there are any actively issued PCNs against your vehicle registration and they will usually respond, I don't believe you would be incriminating yourself in anyway.
I had to do the same a few years ago, i.e. emailed a few council in the areas I drove through asking if there are any active PCNs against my vehicle as I had bought a new vehicle. The seller hadn't done the V5C transfer, had been way over a month, had to call DVLA to get a V5C issued to me and then check if I had incurred any potential penalties active, as vehicle wasn't registered to my name and address during that period so would of been sent to previous owner.
I would say wait for a letter, if you don't receive one within a week or two, you can follow it up if concerned.
Better to follow up such head on if aware rather than dealing with the aftermath of missed fines, accumulated fines etc.