Here's how my spanish bluebells are looking now, and a stalk pulled and placed next to the mystery plant for comparison:
My mystery plant has 5 flowers at the stalk end, whereas my bluebells have considerably more and started lower on the stem. I'm leaning toward blue eyed grass, still comparing to photos. It looks like it had 4 or maybe 5 leaves (some were chewed up) and the leaves are shorter than the flower stalk. At this point, this is a solitary plant. Hopefully it will multiply.