R' Shimon went into hiding along with his son, Elazar. Seeing that so long as anyone knew where they were, they would still be in serious danger, they went to cave. With no other food, they subsisted on the fruit of the carob tree that miraculously grew there and drank water from a stream. They spent all their time -- for the duration of 12 years - immersed in Torah study.
At the end of that time, Eliyahu came and stood at the entrance to the cave and exclaimed, "Who will inform the son of Yochai that the emperor is dead and his decree annulled?" So they emerged. Seeing people engaged in farming, they exclaimed, "They forsake eternal life for temporal life!" Whatever they cast their eyes on would burn. Thereupon a Heavenly voice came forth and cried out, "Have you emerged to destroy My world: Return to your cave!"
So they returned and stayed twelve more months, saying, "The punishment of the wicked in Gehenom is [limited to] twelve months." At the end of that time, a Heavenly voice proclaimed, "Go forth from your cave!"
They went out. Where his son would wound, R' Shimon would heal. He explained, "My son. you and I are sufficient for the world."
On the eve of the Sabbath before sunset they saw an old man holding two bundles of myrtle and running at twilight. What are these for?' they asked him. 'They are in honor of the Sabbath,' he replied. "Would not one suffice? " The man answered, "One is for zachor and one is for shamor." Then R' Shimon declared to his son, "'See how precious are the commandments to Israel!'"
You may have noticed the repetition of rounds of 12, which also echo R' Akiva own paired twelve years of learning and his 12,000 pairs of talmidim. Rabbi Brown explored the significance of that number here: http://kallahmagazine.blogspot.com/2014/05/counting-by-12s-and-lag-bomer.html
So the hadasim are not just there to represent something pretty that people buy for Shabbos but something about the people who buy them. They are not necessarily learned, but they are devoted to doing mitzvos, both the positive and the negative ones. They have that fragrance of goodness. Fragrance is something we appreciate through our sense of smell, the one sense that was not involved in the sin of Adam. There is something of the primordial perfection of man still to be found in scent, and that's one of the things one should appreciate about the fragrant hadas.
Another thing to appreciate about it is how to use vision. Recall that R' Shimon and his son were directed to return to the cave for an additional 12 months because when they first came up they cast their eyes on people and saw only what was lacking rather than what was positive about them. Once they grew wiser, with the addition of another 12 months of study, bringing up to 13 years, they could appreciate the goodness that was not so obvious (one of the points in http://kallahmagazine.blogspot.com/2014/05/counting-by-12s-and-lag-bomer.html).
The two bundles also represent the idea of tying together two apparently contradictory concepts -- the positive mitzvos inherent in the directive of zachor and the negative ones indicated by shamor. The time is also the point of two different day: twilight when Friday is ending and Shabbos is beginning. The man they saw thus symbolized how this world is not just about the temporal existence they despised when they first emerged but about drawing connections between the physical and the spiritual.