I have egg eaters in my flock :evil: but usually they eat all of it, the only clues are white/yolk residue on the nest boxes and all over the remaining eggs with a few remaining eggs having a pea size hole or starburst crack pattern where a beak got it but didn't get it all the way open.
Now, it sounds like the same evidence a raccoon left behind in our coop (I assume raccoon b/c I saw it hanging out in the tree next to the coop... easily could have been a opossum I guess, but I didn't have a visual on one at the time). I found a couple egg shells and that had me on high alert, then one evening we had the door open and I heard them starting to fuss a bit, that's when I found the coon in the tree nearby... it had been several minutes by the time I made it out there, ample time for it to scurry away.