This happened to me last year when I bought a coat. I got it home, and tried it on again and saw the security tag still hanging on it. I didn't even call, I was so mad, I went back to the store and had them remove it. I would think that with it being busy due to the holidays, it's probably not the only one that got left on. Often these stores hire seasonal help and they are still learning the process. I went to Wally World Friday the 18th, stuck 1 box of Capri Sun on the counter, told the cahsier I had 3. When I got home I looked at my receipt and she charge me for 5! I went back a week later, gave them my receipt and say "hey", and they gave me the money back for the 2 I didn't buy, no questions asked. I know stores are cautious for theft & fraud, but I would also imagine this time of year mistakes are being made. I would call the store and tell them, see what they say.
Let us know what happens.