I am glad to hear you are not having pain. To answer your question, yes, it is rare. But you can have dry socket without having pain. Dry socket comes in lots of different forms usually with pain, but sometimes without. If you do warm salt water rinses throughout the day, it will help the dry socket heal faster. You might also want to let the doctor who extracted your tooth know.
Best of luck to you!
William F. Scott IV, DMD