The drawing is actually all there — it’s just that the only thing which shows is what’s on the page. Enlarging the page allows the hole thing to show.
What you have is an outer rectangle which is a path with 4 nodes and six additional objects.
To fix them and combine them into a single path please:
- open in an SVG editor
- select all and set the drawing region to match the paths (in Inkscape this is done by Edit | Select All, File | Document Properties, Resize Page to Content, click Resize Page to Drawing or Selection)
- select and delete extraneous overlapping geometry (the vertical lines of which there are two versions of each)
- draw in a rectangle which reaches from inside one curve to the other (without touching the curves)
- Select the top and bottom curve and the newly drawn connecting rectangle
- Path | Union
- use the node editing tool to delete the extra points which make notches along the sides and then move the resultant curve off point nodes to convert that portion of the paths to straight lines
You might also want to remove the gradient effect which makes the lines light grey.
Once you’re done you’ll have a file like to: