I could even cut a piece of wood and wedge it in there...Half a spring clothespin fits just right.
Or a wad of solder, heated up and poured in to hold it 'just right'.
Or polyester resin...
Lots of ways to 'fix' it. Drill & tap a hole to let a screw hit agonist the front of the takedown lever, forcing it and the lug back.
Or just leave it be...It ain't hurtin' nuthin'...