Hawkins, we will have to agree to disagree on that point in several aspects. To me, this is clearly Jesus quoting scripture that has been lost.
Also, this is not about water coming from rocks. It is about living water coming from the believer. Some would say this is a reference to the Holy Spirit.
Many writings referred to in the Bible have been lost, such as the letter Paul wrote to Corinth before the letter we call 1 Corinthians.
There is no "OT lost writings" from the perspective of OT Canon.
It's not proper to get to conclude that "the verse is not in the Canon" even in the case of missing writings. It is because even when it is a direct quote and the writings are missing, those verses can still be inside the Canon. They are inside the Canon but the original canonical writings are lost. So it's never proper to say that "the verses are not in the Canon".
Jesus was actually extending the OT verses to imply that He's the source of living water. It is because that it is an implication that it is not necessarily be a direct quote.
The following is a reference from a commentary about John 7:38.
College Press NIV Commentary:
In Jesus’ day the Jerusalem celebration of Tabernacles involved a daily fetching of water from the Pool of Siloam in a golden pitcher, and a ritual pouring out of the water at the temple altar. The purpose of this ceremony was to remind the nation of Israel of God’s miraculous provision of
water out of rocks while they were in the desert wilderness (Exod 17:1-7; Num 20:1-11; cf. Deut 8:15; Wisdom 11:4). But for the Jews God’s supplying of water was more than a past, historical event tied to the wilderness experience. The Scriptures repeatedly portrayed God as the one who provides spiritual water to the spiritually thirsty and looked ahead to a time when there would be an ultimate fulfillment of this thirst-quenching. Notice these texts (as well as Ps 107:9; Isa 35:7; cf. Rev 7:14,17; 21:6):
For I will pour water on the thirsty land,
and streams on the dry ground;
I will pour out my Spirit on your offspring,
and my blessing on your descendants.
Isaiah 44:3
Come all you who are thirsty,
Come to the waters;
and you who have no money,
come, buy and eat!
Isaiah 55:1
Jesus echoes Isaiah when he announces, “If a man is thirsty, let him come to me and drink.” John weaves his editorial guidance into the words of Jesus to teach us that neither Tabernacles nor the offer of Jesus were really about water, but about the [Holy] Spirit, whom those who believed in him were later to receive.
Jesus ties this together by describing his offer of water/Spirit as having a scriptural antecedent, streams of living water will flow from within him.
