Yeah, if you're using the Blender MD3 exporter from my plugin suite, that skips non-triangular faces and prints a message about them to the console. So if there are no triangles in the mesh, it will actually export an empty md3, which md3view can't handle (and which isn't of much use anyway). The exporter pretty bad at failing in a noticeable way and could use some work... And the ASE exporter isn't much better, either - it just silently drops any vertices beyond the first 3 from each face.
Since you're talking about backups, you may want to use a version control system like Git for that.