Pictured on your left is the mystery flower, which is a fuchsia-hued blossom with six petals perched atop a grass-like stem that is about three feet in height. I do not recall if I planted a rhizome or a bulb, but I am sure this flower did not develop from seeds.
My initial guess is that this plant is a member of the genus Sisyrinchium, commonly known as "Blue-eyed Grasses," though these are not true grasses. Anyways, feel free to leave your educated guesses in the Comments section.