I had researched this about six years ago.
I found there were a number of gravestones that were broken and lying on the ground. The priests of the day made a list of all the stones that were in want of repair. They then contacted the parishioners they had a mailing list for. Some of the stones were repaired however over the years they had totally lost contact with the many families of Glengarry who had moved on to other locations throughout Canada and the USA. With no way of informing these descendants of the parishoners with damaged stones they made a decision to bury the pieces of stone remaining. Apparently a list of all the stones that were buried was made. Once again disaster struck, the list was kept in the contractors building on the grounds of St. Raphaels. This shed burnt down and the list with it.
This story was explained to me by a local Glengarry historian on one of my visits to the county. I can't recall his name.
That's about all I know about this tragedy.