I would've guessed Ahmedabad or any Station on that route had it been Mumbai Central (MMCT). But since CST is mentioned that is ruled out.
Same day return, since Pune is already completed. Nashik is not in picture as then you would've caught Howrah Mail from there only and you're ruling out Goa route.
I'm out of ideas here. ЁЯдФЁЯШВЁЯШВЁЯЩП
But yes I'll be...
more... waiting for this trip of yours.