At 7th level, when a magus prepares his magus spells, he can decide to expend 1 or more points from his arcane pool, up to his Intelligence bonus. For each point he expends, he can treat any one spell from the magus spell list as if it were in his spellbook and can prepare that spell as normal that day.[...]
A wizard can use the procedure for learning a spell to reconstruct a lost spellbook. If he already has a particular spell prepared, he can write it directly into a new book at the same cost required to write a spell into a spellbook.[...]
(The term wizard seems to mean arcane caster needing a spellbook in this context.)
If my magus uses the class feature knowledge pool to prepare a spell not in his spellbook, can he write that spell in his spellbook using the replacing procedure above? The rulebook talks about reconstructing a lost spellbook, but I don't think still having the spellbook is different from a stolen spellbook or an undamaged one forgotten at the bus stop, magic-wise.