If you don't have your enrolled phone to complete a two-step login with Duo Security, and you haven't got a backup phone defined, you have three options:
- use a (previously generated) backup code that you saved
- enroll a new phone as an alternate and then select it at login
- retrieve your phone
If you hadn't previously generated a list of backup codes, you will need to enroll another device (perhaps your desk phone, etc.) that you have access to, in order to login to an application that is enabled for Two-Step Login.
If you need to enroll an alternate (backup) phone, see http://its.uiowa.edu/support/article/106591 for instructions on how to enroll an additional device in Duo Security. Be aware that you can't enroll a shared phone that someone else has already enrolled in Duo.
After enrolling the alternate device, simply choose that new device from the device drop-down when you're prompted for two-step login verification.
It is highly recommended that you enroll your office phone number as a backup device that you can use in the event that you forget your cell phone at home.