@CrazyShady As with all scripts that use a users hostmask to set a ban, this script uses your ial to get the address.
In case your ial contains no data for a user you are trying to ban, this script will do a /who username to refresh your ial.
If your ial still doesn't return any data for the user in question, the script WILL, as a fail safe, use the nickname instead of the hostmask.
This is probably what happened. It's not a flaw in the script but rather a problem with your ial not staying up to date. This could happen if you have extreme lag causing your ial to be updated on a delayed basis.
If you are having problems with this that are unrelated to lag, please let me know. A small piece of code can fix this problem and make sure your ial stays up to date.