What would seem to be a silly question actually does have some depth to it. I was trying to scoop out some of my favorite soft name-brand ice cream when I noticed it was frozen solid, rather than its usual creamy consistency. After leaving it out for 10 minutes, it was nice and creamy again.
Notably, that amount of time wasn't long enough for it to "melt", as it would still not flow were the container flipped upside down, just long enough to "soften". So why is it that ice cream becomes stiffer/harder when cooled and softer when allowed to warm slightly?
I think the "hardness" of the ice cream is largely determined by the properties of the ice crystals within, which change somehow with temperature. Now while I don't know how they do change, I'm fairly certain of how they don't.
You could view the temperature of the ice cream as infinitely many concentric layers, from a layer of maximum temperature on the outside of the ice cream given the ice cream warms from the outside in, to the point of minimum temperature at roughly the center of the ice cream. Therefore, it's fair to assume that partial melting and therefore decrease in size of each ice crystal is unlikely, as that would require a very thick "band" of ice cream layers to be at a transition temperature between completely crystalline and completely molten, which would only be likely with very slow cooling.