John 6:12
So when they were filled, He said to His disciples,
"Gather up the fragments that remain, so that nothing is lost."
It's right there.
John 10:25-28
Jesus answered them,
"I told you, and you do not believe. The works that I do in My Father's name, they bear witness of Me. But you do not believe, because you are not of My sheep, as I said to you. My sheep hear My voice, and I know them, and they follow Me. And I give them eternal life, and they shall never perish; neither shall anyone snatch them out of My hand.
Notice that He does not say they are not His sheep because they do not believe.
He says they do not believe because they are not His sheep.
Now, none of the fragments will be lost, none of those given to Him are lost, no one can snatch them out of His hand, and none of them have become His sheep by any of their own doing but because they have been given to Him by the Father.
so you demand to know what happen when one sheep wanders off? does the Good Shepard abandon them?
i think you already know.
Matthew 18:12-14
What do you think? If a man has a hundred sheep, and one of them goes astray, does he not leave the ninety-nine and go to the mountains to seek the one that is straying? And if he should find it, assuredly, I say to you, he rejoices more over that [sheep] than over the ninety-nine that did not go astray. Even so it is not the will of your Father who is in heaven that one of these little ones should perish.
He goes after it. He lays down His life for it. does He fail to find it? Nope. Not one fragment is lost, no wolf can snatched it out of His hand, no one can flee from His presence.
Luke 15:4-5
What man of you, having a hundred sheep, if he loses one of them, does not leave the ninety-nine in the wilderness, and go after the one which is lost until he finds it? And when he has found [it,] he lays [it] on his shoulders, rejoicing.
John 6:39
This is the will of the Father who sent Me, that of all He has given Me I should lose nothing, but should raise it up at the last day.