Recovering Lost Mode then Deletion from Find my Iphone
You can use the PIN to unlock the device and connect to the internet (if needed)  

Then open the find my phone app and go to that device.

Tap/select Turn Off Lost Mode

Alternatively, connect it to iTunes to complete the unlock on that device. Worst case, you have a chance to try backing it up (assuming you don't have a current backup). At that point, you can restore the device in iTunes.