This simply means that the relevant package net-tools which includes netstat executable is not installed, thus missing. The package net-tools may not be installed on your system by default so you need to install it manually.

The package also includes aditional utilisties such as arp, ifconfig, netstat, rarp, nameif and route.
To make netstat available on your system simply install the net-tools package using the bellow command:

# apt-get install net-tools