I had the same problem with an SL-D20 I used to have. Not the same dust cover but the same arrangement of tongue-into-hinge that the SL-D2 has.
Because of the design of the tongue, when it breaks off there's a bit left behind: the part where those triangular buttresses occupy the angle between the tongue and the actual lid. On my SL-D20 the tongue was broken off right up to the buttresses but there was still enough left so that it could be inserted into the hinge. Trouble was it would fall out really easily.
There are three ways I thought of to address the problem, two of which I tried. Both worked.
1. Insert what's left of the tongue into the hinge. Then take a fine drill bit and bore a hole through the top of the socket in the hinge and through the tongue on the dust cover but not all the way through the bottom of the hinge. Then insert a pin into the hole, securing the dustcover to the hinge.
2. The hinges on my table eventually fatigued and I installed replacements. Rather than drill a new hole in the new hinge I just wedged some paper, folded to the correct thickness, between the tongue and the interior surface of the socket in the hinge. It worked okay. You had to raise the lid with a bit of care and attention to the task but I do that anyway.
3. I could have glued what was left of the tongue into the hinge. It would have worked fine but there are obvious disadvantages to that approach.
I suspect this relates to your situation. Hope it does and hope it helps.
John