Well, it seems to me we could use the databases that have been suggested. If the goal is to solve the problem, then the citizenship database and the Elections Canada database on where people have voted before would provide us with the evidence of the riding they had been in before they left the country.
There are all sorts of ways in which we could solve this problem without having to try to create a very onerous process of trying to get people to prove it. For instance, people live in rental accommodation. There may be nobody left in the place they lived in two years ago. There could be a very high turnover. In my research on voter registration, I've found that Canadians are incredibly mobile between elections. There's a huge number of people changing their addresses.
Again, I think this is based on an assumption that people are sedentary and stay in one place and not on the kind of dynamic society that Canadian society is today.