Just be glad that it didn't attack the quilt top. My mom always told me find the good in every situation.
Now you can trim away the bad section of the batting and attach a new strip. I like to fuse the join with a 1/2" strip of fusible stableizer or interfacing, then zig zag over the join.
I know you said you had no more batting, but guess you will have to get some.
Oh, and set some traps. LOL