Touch spells, even those specifically channeled through a weapon for purposes of Spellstrike, are retained if the spell does not make contact with the target.
d20pfsrd Spellstrike entry:
At 2nd level, whenever a magus casts a spell with a range of “touch” from the magus spell list, he can deliver the spell through any weapon he is wielding as part of a melee attack. Instead of the free melee touch attack normally allowed to deliver the spell, a magus can make one free melee attack with his weapon (at his highest base attack bonus) as part of casting this spell. If successful, this melee attack deals its normal damage as well as the effects of the spell. If the magus makes this attack in concert with spell combat, this melee attack takes all the penalties accrued by spell combat melee attacks. ...
d20pfsrd Magus FAQ:
...The magus touching his held weapon doesn’t count as “touching anything or anyone” when determining if he discharges the spell. A magus could even use the spellstrike ability, miss with his melee attack to deliver the spell, be disarmed by an opponent (or drop the weapon voluntarily, for whatever reason), and still be holding the charge in his hand, just like a normal spellcaster. Furthermore, the weaponless magus could pick up a weapon (even that same weapon) with that hand without automatically discharging the spell, and then attempt to use the weapon to deliver the spell. However, if the magus touches anything other than a weapon with that hand (such as retrieving a potion), that discharges the spell as normal.
If I'm playing a sixth level Magus, fighting a target with heavy armor and low Dex and I cast Shocking Grasp, followed by my first attack that hits, and then follow up with my free Spellstrike attack that misses by the target's normal AC, but would hit their touch. Would you still retain the charge of Shocking Grasp, would it do it's normal damage without the added weapon damage, or would it be expended with no effect? Normally, touching anything other than your weapon would automatically discharge your spell, but Spellstrike alters the effect of "Touch" to be as part of a normal melee attack, but it does not say if the touch spell needs to be a normal hit, or if it still hits on touch.
So my question is this: If you miss a target by their armor bonus, but still manage to hit their touch, would you retain the charge, would the Shocking Grasp still discharge (doing the spell's damage and not the weapon damage), or would it just discharge with no effect?