coming in another doorway

My app runs fine. It is using something called "passwordless" authentication. I send out emails to employees telling them that they should complete a survey and there is a link in the email for them to do this. An employee clicks on the link and if the email checks out as OK (within a time contraint) they get access to a particular function in my Controller. I have tested this and they get in there fine. The only thing my CI app knows about the guy who just entered is their email address. 

I now need to lookup that email address in one of my tables to get some other information about them. But I have found that coming in by that "side door" means that I don't have access to the database handle I have opened in database.php. Is there some way to communicate the dbase handle, like sticking it in a cookie? Will that work so i don't have to reopen it? One issue is that the main application that opened the dbase handle might not be running (like in the middle of the night). Any suggestions?

Since the proper database.php already exists (although it hasn't been initialized in this case), is there anyway to initialize it? I tried calling l$this->load->database(); but it couldn't find the command "load".  At a minimum, is there stuff I must load first? 

proof that an old dog can learn new tricks