Mystery garden invader

I am curious about a plant that grew up unexpectedly in my garden. If you can identify it, leave a comment.

When a plant that I do not recognize comes up in my garden, I usually let it grow just to see what it will become. In one of my gardens this summer a plant that I thought was a soybean sprouted.

 The seeds look a lot like soybeans but are a different color, a bit smaller, and more irregular. (Soybeans are top left and they mystery beans are lower right.)

 Unlike soybeans, this plant vines. It only got really big in the last month or so when it sent vines out in all directions. Some of them are now six or seven feet long. Also, it appears that some animal has grazed on the plant--there are leaf stalks that appear to have their leaves eaten.

 The beans do not look look like soybeans. They are long and thin, and at first glance appear to be stems.

 There are many flower buds, but I have not found the flowers. Perhaps, though, what I think are buds are really flowers. They seem to have a purplish tint inside.

 I googled "vining soybeans" and "trailing soybean"s and found some entries for plants that are planted for wildlife forage but no pictures that would help me.

Over the years I have planted almost everything that will grow in an Indiana garden. One thing I have not planted are husk tomatoes or ground cherries. (They go by a number of names.) However, I have frequently had the wild version of these plants grow--they are common along roadsides and often are a garden weed. The wild versions ,which are a different species than the cultivated ones, have small berries, unlike the much larger berries that were on this cultivated variety.

Maybe I should try them next year.