SD: I-90 Business Spur (White Lake) unsigned, decommissioned?

[oscar]

Last month, I drove I-90 in South Dakota in both directions between Wall and Mitchell, as well as the business routes I hadn't already covered. Most of the routes in the HB are signed. But I-90BS (White Lake) is unsigned, from both directions of I-90 as well as on the route itself and its intersections with side streets in White Lake.

The AARoads Interstate Guide calls the White Lake spur "retired".

[Highway63]

I don't have any issue with this.