^ Okay but is there a hole where it should (would) have been? If there is no hole I wonder if it's designed to be that way or if it's a manufacturing error where the hole wasn't drilled so the machine putting the assembly together couldn't put the piece in.
If there is a hole it probably broke off at some point. If that's the case I'd try to find some way to add one, possibly using a small engine fuel filter and adapting it to the smaller diameter somehow.