Hi,
Did you really shred his passport
Basically they need to see his old passport to check his period of stay in Canada and if he traveled out of country. To prove that he was present in Canada and he is eligible to renew his PRC, you can show documents such as record from hospital, or bank statements, or if he is staying at senior residence than record of stay can be obtained from there.
You can call them and ask them what other documents they can accept other than passport to check that your father met the basic residency period.
Cheers,