Hi LookingNow,
I’m sorry to hear about all your experiences and I hope you are able to resolve the issue with your mattress.
Yes they would all be enclosed by some type of fabric but the fabric they use to wrap them will vary from manufacturer to manufacturer. Even the pocket coils used in ultra premium mattresses like Hastens or VI Spring are wrapped.
Not all pocket coils are encased with polyfoam for edge support though (see post #2 here).
It’s difficult to find just an innerspring that you can buy individually but there are a couple of sources listed in the components post here that I have confirmed will sell them to a customer although the shipping cost will be high (probably more than the cost of the coil).
It may also be worth talking to Ken at Arizona Premium here who may be able to sell you one of the pocket coils that they use in this mattress which uses firmer coils for edge support instead of polyfoam (you would need to call them to find out) and if they can they would be able to compress it for shipping which would lower the cost.
Phoenix