Are Catholic graveyards prone to falling into disuse and disrepair to the point that no one knows it’s there anymore, annalex? I note that the graves of I believe 13 nuns from this home were relocated from the graveyard at the hospital located about a mile away in 2001, when the hospital closed.
I don’t know if they are “prone”, but it can happen. There are plenty of churches in disrepair as well. Clearly, the misery was great at the time, so you cannot expect them to have been kept up, or even recognized as graves overtime.
It is easier to relocate 12 graves than hundreds of remains in a mass grave.