There were eight circles that needed to be activated at the April event. Six of them, when activated, yielded ritual scrolls that were auctioned off to the groups that were there. What happened to the other two? Did they grow legs and wander off?
There were also some fairly large cards (ie Wererats) that escaped the field with being killed or looted, it's not uncommon for loot/ritual drops to vary where they come from.