Under the old Immigration Act, he may have lost his citizenship. Contact the nearest Canadian Consulate or Embassy and request a "Facilitation Visa" first to see if you are still a Canadian.
You can't lose your citizenship under the Immigration Act, as citizenship has always been under a separate Act. The only way the OP could have lost it was through a formal renunciation. Plus under C-36 anyone who lost their citizenship between 1947 and 1977 automatically had it restored on the 17th April 2009.