I can't be snatched from the Son's hand, not by any individual, Sam Shamoun cannot be snatched from the Son's hand, HOWEVER, I can walk out of the Father's hand and Sam Shamoun can walk out of the Father's hand. Paul is talking about an external thing or person removing the believer, NOT the believer themselves walking out on the Father.
But to say the danger of apostasy is absent from the text is nothing more than an argument from silence. What about Jesus warning to abide in the true vine or else you will be cut off? Again, Remaining and trusting in Christ, not trusting in works, since trusting in works damns you. A piece of fruit cannot grow on it's own or have nutritional value apart from the vine itself. If you cut the fruit from the vine, it will die. There is a risk of being lost and John 6:35-40 doesn't suggest that isn't the case, since later in the context the other disciples abandoned him.
The Father doesn't remove the choice of a person when they come to him, It is his will that none who come to him will perish, but he allows the Christian to either continue to walk in the spirit and remain in him, or he will allow them to renounce him. Again, the choice of the believer is NOT taken away by the Father.
Yes you can technically argue that those who left never believed to begin with but how do you deal with someone who has been in Christ for years, regenerated and born again and falls away? To say there is no possibility of falling away renders the warnings vacuous and pointless.
John Wesley in his explanatory notes had the following to say:
 And Jesus said unto them, I am the bread of life: he that cometh to me shall never hunger; and he that believeth on me shall never thirst.
I am the bread of life — Having and giving life: he that cometh - he that believeth - Equivalent expressions: shall never hunger, thirst - Shall be satisfied, happy, for ever.
 But I said unto you, That ye also have seen me, and believe not.
I have told you — Namely, John 6:26.
 All that the Father giveth me shall come to me; and him that cometh to me I will in no wise cast out.
All that the Father giveth me — All that feel themselves lost, and follow the drawings of the Father, he in a peculiar manner giveth to the Son: will come to me - By faith. And him that thus cometh to me, I will in nowise cast out - I will give him pardon, holiness, and heaven, if he endure to the end-to rejoice in his light.
 And this is the Father's will which hath sent me, that of all which he hath given me I should lose nothing, but should raise it up again at the last day.
Of all which he hath already given me - See John 17:6,12. If they endure to the end. But Judas did not.
 And this is the will of him that sent me, that every one which seeth the Son, and believeth on him, may have everlasting life: and I will raise him up at the last day.
Here is the sum of the three foregoing verses.
This is the will of him that sent me — This is the whole of what I have said: this is the eternal, unchangeable will of God. Every one who truly believeth, shall have everlasting life.
Every one that seeth and believeth — The Jews saw, and yet believed not.
And I will raise him up — As this is the will of him that sent me, I will perform it effectually."
John Wesley's Explanatory Notes: http://www.christnotes.org/commentary.php?com=wes&b=43&c=6
There really isn't much else I can say on this topic at this particular time.