What to do with your hands during a first kiss?

I had a first kiss with a girl after a date we had last weekend. As we kissed I subconsciously rested my hand briefly on her stomach. It went well and she said she had a good time that night, but a few days later after I called to ask her out again, she texted and said that she was too busy to see me anymore. There is a bit of background here, and I think there is a chance that she really is too busy and isn't just blowing me off because of what happened, but I'm still wondering about the way the date ended. Did I make a mistake with the way the kiss went? Did it send the wrong sign? Or am I just overthinking this?