Look at verse 15. Mary Magdalene is crying at the tomb, thinking that Jesus' body has been stolen. Jesus comes up to her and asks why she is crying and for whom she is looking. Then John writes "Thinking he was the gardener..." Mary asks Jesus a question. But I want to key in on the fact that Mary mistakes Jesus for the gardener. Who originally received the occupation of gardener? The answer is in Genesis 2:15 -- The LORD God took the man and put him in the Garden of Eden to work it and take care of it. So Adam was the first gardener. How did he do? Genesis 3 tells that story, but I think John is at least hinting (again) here that Jesus is the "redo" of Adam in the respect that where Adam blew it, Jesus came through. Paul writes something similar in 1 Corinthians 15:20-22 -- But Christ has indeed been raised from the dead, the firstfruits of those who have fallen asleep. For since death came through a man, the resurrection of the dead comes also through a man. For as in Adam all die, so in Christ all will be made alive. That's awesome!
Many have written about this episode in Thomas' life (for the sake of curiosity, "Didymus" means "twin"). I will shorten my comment to this: Thomas' response to Jesus is as direct a "prooftext" as you can get for the divinity of Jesus Christ (which some cults--like Jehovah's Witnesses--deny).
It is also interesting to note verses 30 and 31. John didn't write down everything, but what he did write down he did so that we might believe and in doing so have life in His name. A friend of mine puts it this way. The Bible was written to tell us everything we need to know, not everything we want to know.