There are several quotes in Scripture, which seem not to be found in the Bible, or at least not in one place in the Bible. One example is here:
Mt. 27:9 Then what was spoken by Jeremiah the prophet was fulfilled: “They took the thirty silver coins, the price set on him by the people of Israel, and they used them to buy the potter’s field, as the Lord commanded me.”
Here Matthew attributed a quote to Jeremiah that appears to be from Zechariah.
Mk. 1:2 It is written in Isaiah the prophet: “I will send my messenger ahead of you, who will prepare your way–a voice of one calling in the desert, Prepare the way for the Lord, make straight paths for him.”
And here Mark attributed to Isaiah a combined quote from both Malachi and Isaiah.
“No extant version of Zechariah 11 refers to a field; and Matthew’s attributing the quotation to Jeremiah suggests we ought to look to that book. Jeremiah 19:1-13 (not Jer. 18 or 32) is the obvious candidate. There Jeremiah is told to purchase a potter’s jar and take some elders and priests to the Valley of Ben Hinnom, where he is to warn of the destruction of Jerusalem for her sin, illustrated by smashing the jar. A further linguistic link is ‘innocent blood’ (Jer. 19:4); and thematic links include renaming a locality associated with potters (19:1) with a name (‘Valley of Slaughter’) denoting violence (19:6). The place will henceforth be used as a burial ground (19:11), as a token of God’s judgment. It is fair to say that the quotation appears to refer to Jeremiah 19:1-13 along with phraseology drawn mostly from Zechariah 11:12-13, with the concluding clause used to paraphrase the opening words of Zechariah 11:13: ‘And the Lord said to me.’ Such fusing of sources under one ‘quotation’ is not unknown elsewhere in Scripture (for example, Mt. 2:6, which combines Mic. 5:2 and 2 Sam. 5:2; Mt. 11:10 and Mark 1:2-3, which are a combination of Mal. 3:1 and Ex. 23:20; and 2 Chr. 36:21, which combines Lev. 26:34-35 with Jer. 25:12; 29:10). Jeremiah alone is mentioned, perhaps because he is the more important of the two prophets, and perhaps also because, though Jeremiah 19 is the less obvious reference, it is the more important as to prophecy and fulfillment.” (Expositor’s Bible Commentary, Tyndale commentary)