I tried a few spots to the south trying to intercept it again but didn't find it.
Rhoda and I later walked the breakwall at New Buffalo looking for Purple Sandpiper. We didn't see any but a couple times medium-sized calidrid sandpipers did flush, the much more common Dunlin. Two at the very end were fairly cooperative.
This bird was noticeably larger than the other, I'm presuming adult vs first winter (but I suppose it could be a sex difference as well)