One should never run into this situation if he/she planned it well (i.e. listed at least 6 -7 preferences with some courses that he/she could get in if all else fails).

Should no offer arrive, one can either wait another year and apply again or pick a TAFE course then transfer to uni. Alternatively, contact the uni(s) of interest to see if something can be done (highly improbable that there is some success but doesn't hurt to try, as well as gets some advice from the uni itself).