Why is there no crater on the focus terrain on Pluto?

It is interesting to see mountains and flat plain on the latest photograph with no impact crater on the Pluto's surface. According to the NASA scientists' explanation, it is probably of recent geological formation perhaps less than 100 million years and perhaps it is still geologically active.

I was thinking that, since Pluto is so cold (about -230degC), any impact by icy asteroid will create great heat, melt the asteroid and the surrounding impact area, resulting in liquid water, liquid methane, etc, which would immediately submerge any crater formed. As the atmosphere is so cold, the liquid will turn into ice soon and the surface would be covered up again, leaving no trace of crater. 

Couldn't it happen?