Recent device update? Was there one for the Amazon devices? Because the most recent public software for the Almond 3 was in January. I only have one Echo and have not had any problems with devices.
Did you try rebooting your Almond 3, then rebooting the dot once the Almond is back up? After that does it show in the devices list at all? I know my Echo got confused after a power failure last year one time. Had to add it back on the network after a reboot, but nothing major.