The Bible refers to several texts that are no longer extant, such as the Book of the Wars of the Lord, or the Book of the Acts of Solomon, for example, which we usually refer to as lost scripture. We generally do not think of many of the texts within the Bible as being incomplete in themselves, thus comprising another segment of lost scripture as well. Patrick D. Miller, Jr. and J.J.M. Roberts provide some interesting food for thought when it comes to 1 Samuel and the "ark narrative":
...it is difficult to regard 1 Sam 4:1b as a natural beginning [of the ark narrative, as many scholars do] for the following supposedly independent, complete, and self-contained narrative. Too many questions are left unanswered. Why, for instance are the Israelites defeated? That the Israelites do not know the reason creates no difficulty--a similar motif occurs elsewhere (in the story of the defeat at Ai, for example)--but that the reader-- or hearer, as the case may be--is given no explanation for this unexpected course of events is quite strange. There are few, if any, analogies for such a narrative technique in the Old Testament, and whatever analogies might be cited seem to be cancelled out when the writer adds a second defeat involving the loss of the ark and the death of the priests of Yahweh. Where else in Old Testament literature does one simply narrate such a devastating blow to Israelite piety without any attempt at theological explanation? Moreover, who are Eli, Hophni, and Phinehas? The narrator introduces them in 4:4 as though they were already well-known by the reader. This would seem to imply the existence of a preceding narrative about them. It has also been suggested, though this is not absolutely necessary, that Eli's anxiety over the ark in 4:13 presupposes a similarly missing background.
In other words, to make the ark narrative a complete, self-contained unit, one must supplement Rost's text [the ark narrative beginning with 1 Sam 4:1b] with a tradition introducing the main characters and alerting the reader to Yahweh's displeasure toward Israel. The tradition of the wickedness of Eli's sons (1 Sam 2:12-17, 22-25) would fill part of that need. It would explain the reason for Yahweh's anger and, in particular, why his anger reached even the priests and led to the loss of Israel's most sacred cult object [the ark]. It would also be an adequate introduction to the sons of Eli, though one would still lack an introduction to Eli himself. One must question whether that part of the original ark narrative may be reconstructed from the present text of Samuel. It would appear that the original beginning of the ark narrative has been fragmented and partly lost by the secondary insertion of the traditions about Samuel's childhood.
This is where we differ from Willis. He regards the present form of 1 Sam 1-7, including the Samuel traditions, as an original, integral unity. Though his analysis is suggestive for interpreting the present form of the text, such unity it now possesses is clearly redactional, not original. Considering the major role Samuel plays in the present form of 1 Sam 1-3, the total omission of any mention of him in 4:1b-7:1 is certainly striking--particularly since 3:21 states that Yahweh continued to reveal himself to the now famous Samuel in Shilo--and suggests that these two sections in their present form could not be an original unity.
Patrick D. Miller, Jr., and J.J.M. Roberts, The Hand of the Lord: A Reassessment of the "Ark Narrative" of 1 Samuel (Atlanta, GA: Society of Biblical Literature, 2008), 27-29