You don't actually add /sbin/script in your path.. if the script resides in /sbin, just having /sbin in your path will find that executable, if you did make it executable.
Okay, I read it wrong, thought you made a script called script.. not a directory.
Well if you added it, did you export it after saving the profile file?
source /etc/profile
Will reread the file and make the changes in real time..