Old iPhone 5c showing up as "My Devices" in iCloud
Here's something that's perplexing me and I wonder if anyone else has had this issue. When I log onto iCloud on my iMac via Safari and go into the settings section, I see a list of all my current devices along with old my iPhone 5c which I gave back to Verizon when I got my iPhone 6. It says "You are currently signed. In and running iOS or OS X Yosemite on these devices." It's got my iMac, iPad, and current iPhone 6 correctly listed but gives me no option to remove the 5c.
I recall deleting all contents of the phone and switching off Find My iPhone prior handing it back in, so I'm not sure why it's still there. It doesn't appear when I actually open find my iPhone nor does it pop up when I look into devices associated with my iTunes account. I certainly don't want it still attached to my account as I don't know where that phone will end up. Is this an issue similar to the iCloud tabs issue where it takes s few weeks to remove itself after inactivity or something else?