Well...depending on your seniority, if the hours have been cut back and you don't go in, you could be the first to be let go (IF that happens).

Is this a temporary January-slow-retail move or long-term?

Someone made a mistake and didn't call you. I guess - ask if this will matter in 50 years? You may well be right - but that won't pay the bills!

Forgive the boo boo, and go in. JMO

(And start checking the help wanted ads if the short hours are going to be a permanent arrangement).