Can't tell from the photo if that block of metal on the strap is a packing piece or was attached to the subframe with a stud fixed in it that the strap fastens to. You might just be lucky and its s sheared bolt and the lump is just a thick washer.
You need to get back underneath and take the bolt/stud and lump off the strap and see what you've got. Then swing the strap around and look for a fixing point (the other half of a sheared bolt or less corroded bit where the lump was welded on) within the arc of the strap - remember chances are the strap was not tight.
The little lugs are welded onto the subframe for speed of assembly so it might be more fiddly but if you can get a bolt through another hole (in the same component and without fouling anything that moves) clean the surfaces to get a good electrical contact and bolt it back.
Or just send us soem more photos so we can suggest fixing points.
