Alienware 17R4 i7 Core-7820HK CPU @ 2.90 GHz
Graphics GTX 1080 8GB
Character and Armature created in 2.79, but opened in to 2.8 for final render.
Half the armature is gone, (Bob.Armature.Rig) or invisible, and the other half is fine (Bob.Face.Rig) but according to animation it is still present somewhere in my file, since the keyframes still produce movement on hands, arms and shoulders.
Now under my Scene the Armatures are named "Bob.Armature.Rig" and "Bob.Face.Rig", and you can open this in 2.79 to see its functional state, but if opened in 2.8 the rig breaks as described.
Since Spring had been in production for a while, i assume you may have seen this issue while transferring from 2.79 to 2.80