You cannot use the DIR TO function to fly to a point in the alternate flightplan (it is disabled). You'd have to enable the altn in order to make that work.
Was the VOR you were cleared to overhead the airport? What happened was probably the FMGS going into the done phase thinking that you've landed already. In the done phase everything is dumped. Happens all the time with guys activating the secondary when still not properly established on downwind during circling approaches.