Perfect timing

Thursday my students had to practice their writing skills and all had to explain the same writing prompt:

You buy some balloons that look nice, it's cold outside and on way they start sinking and getting wrinkled, but when you get home into your warm house the balloon returns to normal. Explain.

So yesterday, girl comes into class all excited proclaiming, "Mister, it actually happened like yesterday!"

I'm confused, "what happened?"

I was with my friend yesterday and she bought a balloon, and while we were waiting at the bus stop, she got upset because her balloon started sinking. I told, 'don't worry it'll be okay when we get home!'