Slow Shower Drain Problems

[Sheepdog]

My shower drain seemed to be plugged up as it would drain very slow and the tub would get a couple inches of water in it when showering. So I bought a little plastic barbed snake stick and tried to clean it out. Mistake!
Apparently there is no p-trap on mine and there is some kind of a rubber one way valve bladder in the drain which caught on my snake and came out in ripped up tiny pieces! Now, if you don't stop up the drain and the Gray tank valve is open and connected to the sewer, you get a back up of nice smelling sewer gas in the shower. This took me a few months to figure out where the smell was coming from- nice!!! So now I keep the Gray valve closed and the drain stop down in the shower until I can fix it. Looked in the basement and it looks like there is a plastic tube connected in the drain which is probably where the rubber one way valve was located, but haven't removed it yet.
Anyone know anything about this?
For those of you out there with slow draining showers , DON'T snake your shower drain!!!