Then, when Jesus was raised from the dead, his disciples remembered [ἐμνήσθησαν; emnēsthēsan] that he said this, and they believed the scripture as well as the word Jesus had spoken. (John 2.21)
His disciples did not understand these things at first, but when Jesus had been glorified, then they remembered [ἐμνήσθησαν; emnēsthēsan] that these things were written about him, and that they did these things to him. (John 12.16)
Of course, the reference to the disciples later remembering what Jesus had said/done in John 2 comes at the end of John's account of the Temple incident, and especially Jesus' answer to "the Jews," "Destroy this temple, and in three days I will raise it" (2.19). In John 12 the events that were later remembered concerned Jesus' entry into Jerusalem amidst acclaims of blessing as the one who comes in the name of the Lord. These are clearly pivotal events in the Fourth Gospel's account of Jesus' life, and the evangelist explicitly acknowledges that, beyond actually witnessing Jesus' ministry, "remembering" Jesus' life from a perspective informed by (i) the resurrection and (ii) the Paraclete [= Holy Spirit] are crucial for anyone wanting to properly understand Jesus.
As I was reading Craig Koester's The Word of Life: A Theology of John's Gospel (Grand Rapids and Cambridge: Eerdmans, 2008), a question stuck in my head. First, the passage from Koester responsible for making me think:
Jesus speaks of dying as the act of giving his flesh. He tells the crowd that what "I give for the life of the world is my flesh" (6:51). In what follows, Jesus speaks of those who eat his flesh and drink his blood, using disturbingly graphic terms to underscore the reality of his death (6:53–56). . . . [Many] recognize that the primary level of meaning concerns crucifixion, which is the way Jesus' flesh is given and his blood is shed." (84)
In John's gospel, Jesus says a lot of difficult things, whether about eating his flesh and drinking his blood, as here, or about living water flowing out of people, or those who oppose him being the children of the devil, and so on. What surprises me, however, is that the evangelist doesn't add more comments that later, after Jesus had appeared to his followers raised from the dead, that then they understood his comment about eating his flesh and drinking his blood. How appropriate it would have been, in my opinion, for the narrator to have added the words in bold:
Then Jesus said to them, "Verily, verily I tell you: Unless you eat the Son of Man's flesh and drink his blood, you do not have life among you. But whoever eats my flesh and drinks my blood does have eternal life, and I will raise him up on the last day. For my flesh is true food, and my blood is true drink. Whoever eats my flesh and drinks my blood remains in me and I in them." His disciples had no clue what Jesus was talking about, but later, when he had been raised from the dead and had explained the Law and the prophets to them, they remembered his words and rejoiced. (John 6.53–56, and then some)
But John doesn't say that, and I'm a little intrigued why not. There are no answers to this question, of course; John also never tells us if Jesus ever got indigestion or if he ever sneezed so hard it hurt his back. But from where I sit, Jesus' words in John 6 are much more difficult to "remember" than his statement in the Temple or his acclamation on the road into Jerusalem. But I think one point is fairly clear: In order to read the whole gospel properly, the evangelist intends us to remember every pericope, every paragraph, even every word, with the enhanced memory informed by Jesus' resurrection and the guidance of the Counselor who comes in Jesus' absence (John 15.26–27).