Dang, where’d that go?

I was stripping down this bike to give it a good deep clean when I noticed that not only was the derailleur hanger grimy, it was loose. so I took it off to clean underneath the derailer hanger a good wipe down and then add some thread locker so the two-part bolt does not come loose.

Well, now I can’t find the threaded part. I still have the part that goes on the inside of the frame and I have the hanger.

Are those pretty uniform even though each hanger is unique? Would one of those bolts and caps to a different hangar work?

They look kind of like the ones you used to hold a chain ring on the spider, are those an alternative?