Yup, your mussel passed on.

I've done a bunch of research on mussels and I think our
garden ponds are too small and too warm for them. Some
like rivers and some like ponds. Some are so picky that
they won't reproduce without a certain kinf of fish for
their babies to parasite. We have the most diverse population
of mussels in the world. Something like 55 species to the
Old World's 12.
Unfortunately the zebra mussel is moving in and causing
havoc with native species. They can actually cover a native
mussel and cause it to starve to death.

kathy :-)