I didn't want to have to ask for help, but I looked through the forum and can't find the answer I'm looking for. I just got through the sewers, and I'm assuming that I've found the item for the sidequest there, which I think is the Odd Keystone. I've gone back to the sewers though, and I searched for the guy on the phone and I just can't seem to find him. Do I have the wrong item, or am I just not looking hard enough?
EDIT: Well, this is a little embarrassing. Literally, less than 30 seconds after posting my question I found the guy. Sorry about this lol.