Hi EZ4HZ,
While it’s certainly not my area of specialty … there is more information in post #7 here and the posts it links to about sheets and fabrics that may be helpful and there are links to two topics at the end of the post that discuss linen sheets as well. Our next sheet purchase will "hopefully be a set of linen sheets from rough linen but that is some distance away yet. In “theory” … they would be thicker than regular cotton sheets (or bamboo blend sheets) so they would probably have more effect on the “feel” and contouring of the memory foam but I don’t have any personal experience with the combination.
Hopefully some of the members here that own linen sheets (Restoration Hardware or otherwise) or use them on a memory foam bed will see your post and provide some further comments and feedback.
Phoenix