Going back to the topic , If it was just your dad who saw the priest then try to find out if he can see other ghosts . Your dad just might be a "sensitive" psychic and not know it !
I know for fact he's seen other ghosts.
Trouble is I can't remember the stories that well, he has a tendency to tell stories about what happened somewhere when drives through or past the place where the event occured. As I haven't lived with my parents for years, it's a long time since I had the chance to hear the stories The ones I remember as the ones I've heard within the past few years.
I've got one quick one.
This goes back a good few years (quite when exactly I can't remember). One summer we were staying with my aunt, and my dad was in the yard of their farmhouse and saw a woman walking down the lane to the farm. He looked away, looked back and she was gone. She hadn't gone into my Aunt's house, she hadn't gone into my Uncle's farmhouse (which is more or less next door)!
However with this story there is plenty good reasons for ghostly happenings, firstly both of the houses overlook the cemetary of the nearby town/village. Secondly (and more importantly) the farm is in continental Europe rather than the UK, so has seen various WWII battles between the Allies and the Nazi's, including one that took place in the fields between the village and their farm.
Why a woman not a soldier, maybe a woman died during a skirmish whilst trying to reach safety?