Смотря куда выехал... Если в США, то нет проблем вернуться с действующей одноразовой визой.
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A single entry visa allows you to come to Canada only one time. Once you have left Canada, excluding travel to the United States and St. Pierre and Miquelon, you will need a new visa to travel back to and enter Canada.

If your visa is still valid and you are travelling only and directly to the United States (including its Territories and Possessions) or St. Pierre and Miquelon, you do not need a new visitor visa to return to Canada. If your visa expires before returning to Canada from one of these areas, and you are not in possession of a valid visitor record, work permit, study permit, or temporary resident permit (authorizing re-entry), you will need to get a new visitor visa.