This verse identifies the location and timing of those scriptures.
Surah 2:41:
And believe in that which I reveal, CONFIRMIMG that which ye possess already, and be not first to disbelieve therein, and part not with My revelations for a trifling price, and keep your duty unto Me.
The Quran does not say it confirms "the original Injil that was lost." It uses the present-tense prepositional phrase "with you" or "possess already".
The Fact:
In the 7th century, the "People of the Book" possessed the same Bible we have today (as evidenced by the Codex Sinaiticus, Vaticanus, and various Syriac/Latin manuscripts).
If the Quran confirms what was "with them" in the 7th century, it is CONFIRMING the actual Bible—complete with the Trinity, the Deity of Christ, and the Crucifixion—all of which the Quran elsewhere denies.
If a Muslim argues that the Bible was already corrupted by the 7th century, Surah 2:41 makes the Quran a "confirmer of corruption."
If the book "with them" was a lie, then the Quran, by "confirming" it, is also confirming a lie.
If the Quran is the "Word of God" and is incapable of error, then its confirmation of the book "with them" proves that the 7th-century Bible was the authentic Word of God.
The end of the verse warns the People of the Book not to be the "first to disbelieve" in the Quran. The only reason they would disbelieve is that the Quran contradicts the very book it claims to confirm.
Christians Ask: "If the Quran CONFIRMS my book, and my book says God has a Son, why does the Quran then tell me I'm a disbeliever for believing my book?"
Surah 2:41 prevents the usual "Escape to the Original" tactic.
When a Muslim claims the Bible is changed, Christians point to this verse and ask the question:
"Does the Quran confirm what was WITH them in the 7th century, or what was NOT with them?"