Awkward...

Today I had a rather awkward, unexpected experience. I had expected to be going to an early Chanukah dinner with my sister and my dad, and we were to exchange gifts. So, I went out and bought gifts for the two of them. However, when I walked out get in the car, I saw that my step mom was also there too. Here comes the awkward part comes in-I had no gift for her. So, I casually left my dad's present in the back of the car and gave my sister her present later. But this left me wondering: What would the best way to handle this situation?