Missing completed plans

Has anyone else noticed that some of their completed plans are not shown in that list under the Plans tab even though you never explicitly dismissed them?

I have a feeling this is a bug, but maybe there is some setting I don’t know about. I don’t think it is old ones that go away after a period of time since I have a few that are hanging around which are very old.

I have a vague half-remembered idea that there is a limit of the number of Plans that can be displayed on the page. If you go over the limit, not all will display. If you then delete one and refresh, one of the undisplayed ones will re-appear. I’ve since tried to consolidate several of my completed plans (which I use as post-it notes).