Sorry, I misspoke. They rose and broke away from the Jedi Order aproximately 2,000 years before TPM. The "war" between the Sith and the Jedi (and the Sith and themselves) lasted 1,000 years, at the end of which the Sith were thought to have become extinct. So for a thousand years (up until Darth Maul's appearance), the Jedi Order assumed the Sith were history. But in reality, Darth Bane had merely started the "rule of two" and kept the Sith in hiding.
That's all according to the TPM novelisation, and it was the first source to posit such a backstory for the Sith.
Not really a blip (especially if the war lasted as long as the Republic's lifespan, even though it took place before the Republic's foundation via the AOTC chronology), but certainly not the 5,000+ timespan of Sith-involved galactic wars and empires talked about in pre-1999 comics. The prequels have given us a thousand year Republic that was formed after the last "full scale war" before the Clone Wars, and the Sith have a 2,000 year history prior to the movies, half of which was spent in hiding without the knowledge of the Jedi.