Default [Q] Tried to update ATT G2 booted into TWRP, unable leave TWRP or go to Download mode

When I got my ATT G2 I rooted it, and installed TWRP custom Recovery. A week ago I got a system update notification, without thinking I updated the phone. It rebooted into TWRP recovery, and all I can do is navigate around the Recovery. I factory restored my phone, so I don't have SU, and I can't enter download mode. Any ideas on how I can fix my phone, or go about getting it replace?