Given that non-flexible fares are almost always substantially cheaper (and that most budget airline fares are automatically non-flexible), it is inevitable that one day you will be unable to fly on a non-refundable ticket.
While the fare in these circumstances is almost always non-refundable, the taxes remain fully refundable.
So, if this ever happens to you, you should always contact the airline in order to obtain this refund (normally onto the same crdit/debit card that you booked the flight with).
In the case of Air Malta, this involves calling them on 2166 2211, with your booking reference, to process the refund. Air Malta should be commended for the relative ease of obtaining such refunds, and the fact that they do not make an administration charge.
(Needless to say Ryanair will charge you an admin fee of €20 for any such claim. You also need to send it in writing to their head office: Ryanair Limited, Corporate Head Office, Dublin Airport, Co. Dublin, Ireland).