The regulation states:
Article 8 - Right to reimbursement or re-routing
1. Where reference is made to this Article, passengers shall be offered the choice between:
(a) - reimbursement within seven days, by the means provided for in Article 7(3), of the full cost of the ticket at the price at which it was bought, for the part or parts of the journey not made, and for the part or parts already made if the flight is no longer serving any purpose in relation to the passenger's original travel plan, together with, when relevant,
- a return flight to the first point of departure, at the earliest opportunity;
(b) re-routing, under comparable transport conditions, to their final destination at the earliest opportunity; or
(c) re-routing, under comparable transport conditions, to their final destination at a later date at the passenger's convenience, subject to availability of seats.
So indeed you should be refunded the cost of your ticket.
It is a bit unclear form your post what exactly happened, when did you know about the delay, etc, although generally since you didn't take a later flight/re-route then there is no duty of care.
Note that the airline is not obliged to re-route you on a flight of your choosing, and many "low-cost/charter" airlines will re-route you on the next available flight on their own metal, which in you case seemed to have been available one day later.