$14000.00 from the government and they deny it?

My mother ped away and $14000.00 appeared in her bank account, and they can't trace it .... Has this ever happened to anyone? The deposit says it came from CPP Canada, so I called them, and they DENIED it. Then, the regular Revenue Canada line denied it too. My mother did not have any death benefits and did not pay into CPP - they did not even cover her funeral. Where did this money come from? I'm scared to spend it because then Revenue Canada will want it back.