Dear Killabee,Ibn Saba'a never existed ,I will give you my reasons:
the story is originated by Saif Bin Umer Al-Timimy who lived in the second century A.H 100 years after Ibn Saba'a.While the existence of a person in the name of Abdullah Ibn Saba in the early history of Islam is seriously under question,so I don't know from where Umer took his sources.
Sayf Ibn Umar distorted the biographies of the companions of the Holy
Prophet (PBUH&HF) to please the government of his time, and to distort the history of Shia and to ridicule Islam.
it is just a tale,The tale of Abdullah Ibn Saba is over twelve centuries old. Historians and writers, one after the other recorded it, adding more and more to it.
With a glance at the chain of transmitters of this story, you will find the
name of Sayf sitting in there. The following historians recorded directly
from Sayf:
1) Tabari.
(2) Dhahabi. He has also cited from Tabari.
(3) Ibn Abi Bakir. He has also recorded from Ibn Athir,who has
recorded from Tabari.
(4) Ibn Asakir.
So he was the Only source for those (great Historians)the tell the story through his only.
Therefore, Sayf's character and his history should be studied and analyzed with a great care.
Sayf wrote the following two books which
were available even during the reign of Umayad:
1. "al-Fotooh wa al-Riddah" which is the history of the period before the
death of the Prophet (PBUH&HF) until the third Caliph Uthman resumed
office as the ruler of Muslim world.
2. "al-Jamal wa Maseeri Aisha wa Ali" which is the history from the
murder of Uthman to the battle of Jamal (the fight that happened
between Imam Ali and some companions).
These books are now lost but survived for a number of centuries after
Sayf's own lifetime. Based on what we found, the last person who had said
that he had possessed Sayf's books was Ibn Hajar al-Asqalani (d. 852 AH).
The following leading Sunni scholars confirm that Sayf Ibn Umar was a well-known liar and untrustworthy:
(1) al-Hakim (d. 405 AH) wrote: "Sayf is accused of being a heretic. His
narrations are abandoned."
(2) al-Nisa'i (d. 303 AH) wrote: "Sayf's narrations are weak and they
should be disregarded because he was unreliable and untrustworthy."
(3) Yahya Ibn Mueen (d. 233 AH) wrote: "Sayf's narrations are weak and
useless."
(4) Abu Hatam (d. 277 AH) wrote: "Sayf's Hadith is rejected."
(5) Ibn Abi Hatam (d. 327 AH) wrote: "Scholars have abandoned Sayf's
narrations."
(6) Abu Dawud (d. 316 AH) wrote: "Sayf is nothing. He was a liar. Some of
his Hadiths were conveyed and the majority of them are denied."
(7) Ibn Habban (d. 354 AH) wrote: "Sayf attributed fabricated traditions
to the good reporters. He was accused of being a heretic and a liar."
(8) Ibn Abd al-Barr (d. 462 AH) mentined in his writing abut al-Qa'qa:
"Sayf reported that al-Qa'qa Said: I attended the death of the Prophet
Muhammad." Ibn Adb al-Barr continued: "Ibn Abu Hatam said: Sayf is
weak. Thus, what was conveyed of the presence of al-Qa'qa at the death
of the Prophet is rejected. We mentioned the Sayf's traditions for
knowledge only."
(9) al-Darqutini (d. 385 AH) wrote: "Sayf is weak".
(10) Firoozabadi (d. 817 AH) in "Towalif" mentioned Sayf and some others by
saying: "They are weak."
(11) Ibn al-Sakan (d. 353 AH) wrote: "Sayf is weak."
(12) Safi al-Din (d. 923 AH) wrote: "Sayf is considered weak."
(13) Ibn Udei (d. 365 AH) wrote about Sayf: "He is weak. Some of his
narrations are famous yet the majority of his narrations are
disgraceful and not followed."
(14) al-Suyuti (d. 900 AH) wrote: "Sayf's Hadith is weak."
(15) Ibn Hajar al-Asqalani (d. 852 AH) wrote after mentioning a tradition:
"Many reporters of this tradition are weak, and the weakest among them is Sayf."
in modern time:
In recent years some scholars have questioned the existence of Abdullah Ibn Saba. Taha Husayn, an Egyptian scholar believed that Ibn Saba was a fictitious character invented by groups opposed to Shi'ism. Ali al-Wardi, professor of history at Baghdad University wrote that "it is claimed that Ibn Saba' incited unrest, but no such person ever existed." Most modern twelver Shia deny the existence of Ibn Saba. The first book of Murtadha Askari in this field, titled "Abdullah Ibn Saba" which was published in 1954. He theorized that Sayf Ibn Omar al-Tamimi made up Abdullah ibn Saba.
if you have any question my friend be free to ask it.