I had to go hunt down the review to this show to figure out whether or not I missed something. Turns out, I didn't.
For starters, every show or movie in the past 10 years where the police are trying to track someone down who has a cell phone, has been able to triangulate their position based on the three closest cell phone towers. Mac had Joe's cell phone number, this one should have been a no brainer. Very poorly written plot device. They had to keep him on the phone? Only to trace an unknown caller. Mac was calling him, not vice versa.
I don't understand why Joe was even in the bank in the first place. Trying to prove his innocence in the murder? Gimme a break... If this was a plan to rob a bank, you don't go back after the robbery. No explanation whatsoever. I suppose we're expected to believe that he was trying to get the money after Derek failed to get it, but we already saw he was planning on meeting up with Derek later.
Also, why would Derek leave the money in the bank? Was he planning on going back to get it later? Right... Everyone knows that banks are so easy to break into!
Maybe the writers were on strike for too long before writing this episode. I usually find some silver lining, but this officially sucked.