Using Pro v19.2.222 64bit Windows 7. I created a fairly simple component, saved it, and while my back was turned it disappeared. Well, not exactly. It’s still listed in the Component window, and the statistics show multiple instances, and lots of faces and edges. But they’re all invisible. I’ve done the Unhide All. All the other components in the file are visible. I can drop another instance of this component into the drawing and see its blue bounding box, and move it around, but there is nothing inside. And as soon as I deselect it, it disappears and cannot be re-selected. Yet the statistics affirm their existence.
Sounds like you hid the contents of the component. To unhide them you would need to first open the component for editing. Probably the easiest option would be to select the component in Outliner, and open it for editing. In the View menu turn on Hidden Geometry. Then select all of the geometry and in Edit, choose Unhide.
Thanks, Dave. You nailed it.