In my experience this will always require recovery since all of the data file's SCNs must be synced to open Oracle. I think his site would have had to be totally inactive for it not to need recovery, even if he has all of the data files. If it was active and not in archivelog mode, wouldn't he be required to go back to a previous cold backup?
I usually use this process (recreating the control file) to refresh test databases from running production ones, which always requires recovery. But Oracle is pretty robust in this manner, so hopefully it will have a happy ending...
