If the clips were imported from the PC into Videopad and the project was subsequently saved, then VP should know where they are. When reloading a project, if VP can't find clips it will prompt the have them manually located. Have never witnessed 'red exclamation points or triangles' here.
Take a screen shot, upload it to a free server, get a shareable (public) link, copy the link and post it here. Perhaps that will jog someone's memory.
Of course. Save Project File AS routinely, giving it a unique # or name, so as not to overwrite prior saves. Using Save Project Files (no AS) will overwrite. Then you can restore a project to the state it was in when saved. Just double-click the VPJ file (which isn't playable).