Plato was missing for a fortnight, and just as I thought he was gone for ever neighbours spotted him settling in to a feral colony. He was the same age then as harry is now. Plato is still with us and is approximately 14.
Is Harry a complete male as they are more likely to roam particularly as there are likely to be many queen cats in season at this time of year?
Local vets and animal shelters will tell you if is bad news, but as he is male complete or neutered, up until you know he is dead do not give up hope.
I do feel for you. We were very sad when Plato was missing.
My sister's cat was found after two weeks too... hang in there, a mum!