I don’t really follow why you’re involving Hazel and the file system for this?
Why not just:
Trigger macro every minute
If [wireless network "blah" is connected](http://wiki.keyboardmaestro.com/condition/Wireless_Network)
Set variable "Wireless Network Missing" to 0
Else
Set variable "Wireless Network Missing" to calculation "Wireless Network Missing + 1"
If calculation Wireless Network Missing > 3 then
Panic!
Else
Notify "Trouble?"