A lease, mail that you have received, credit card bills, bank statements, phone/cable bills.. lots of ways to prove presence if you're really living here.
You should look up whether you have been meeting the residency requirements to receive healthcare because I assume you had your children in Canada. Even with a valid health card you may not have been entitled to healthcare. If you were receiving child tax benefit or welfare your absence from Canada could also mean you were not entitled to receive any of these payments. All depends on how much time you spent out of Canada and when.
