I snaked a bathtub drain with auger,
And now the cable won't come out
As it seems to be snagged by a
Spring-loaded check valve just inside the tub.

How do I extricate cable?

Reverse direction while you're pulling back. Tell me exactly just where you went down with the auger. Through the drain or the overflow. Good luck, Tom

You E-mailed me that you went down the over flow. What type overflow do you have? )(see images) Is it possible that you have a older house with a drum trap, (see image) instead of a "P" trap and you're hung up there? Regards, Tom