Yes, Sansevierias do flower on occasion when they're mature plants. The long, slender flower stalk is generally topped with a cluster of whitish tubular flowers. Sometimes they're intensely fragrant.

Does the flower start off yellow?
I can't figure what this yellow thing is comming out of the soil.

If it's coming out of the soil, it could be an offset.

All the flowers I've seen emerge from the center of the rosette of leaves.

If it's a bright yellow, it could be a variety of mushroom that commonly occurs on potting soil. If so, you'll know in short order because the things grow very fast. If it is a mushroom, get rid of it ASAP. It won't harm the plant, but spores are produced quickly & you'll have repeat performances at regular intervals. Let us know what it turns out to be . . .