Stuck case in 35 Whelan TC Encore

A couple of points, but it's hard to say without seeing it. How hot is your load?
You might want to try setting the shoulder ahead, your separation might have been caused by too much space ahead of the shoulder. Neck sizing might be a good idea...

Do you anneal? it might be a good idea to keep your case necks from work hardening.

How many firings do you think that case had on it?

With an Encore, you are headpacing on the shoulder, right?

Case head separation normally happens when your pushing the shoulder back too far. The over working/expanding (stretching) of the brass causes it too fail. Annealing brass help prevent brass from splitting but does very little in stopping improper setup of the sizing die. With a bolt gun (single shot) you only need to set the shoulder back 0.001"-0.002" and no more. With a simi-auto It needs to be pushed back 0.002"-0.003" (SAAMI spec) for reliable feeding. Case gauges are good for checking sized brass for simi-auto. On a belted case I size them like a bolt gun.

A lot of times you can use a bore brush to extract the broken piece. You push it in till it contacts the brass then pull back. Since the bristles do not easily change directions it will grab and remove the piece.