"both spells automatically negate each other with no other results."
In my games, the chronomancer could regain it, but I could see a GM declare that it technically negated a spell, and thus couldn't. Of course, if you cast a scorching ray on an unaware red dragon, you just made it aware of your presence, which a GM could declare as an effect if they wanted. Or even "oh, that adventurer can cast that spell" increased their understanding/knowledge, so no rewind. I'd suggest reading it as if the spell had any of its text based effects. ot may cause corner case oddities, but is the simplest to adjudicate.
