The seam is actually invisible because it was pieced, it was sewn to the next piece then folded over. So I don't think I can use the ladder stitch on it because I don't have two "sides" to connect really. I hope I'm explaining this well.
I did get the Dritz Stitch Witchery and pressed it underneath the fabric edge which had popped out, and again under that to hold the fold down, and I'm guessing I'll need to topstitch over it, so I bought some invisible thread. I might just make a tiny straight seam with my machine, since I have not decided whether I am going to quilt over the entire blue portion of the top.
I previously planned to just FMQ flowers sporadically, following the design on the backing fabric which will be the same as the large outer border on front.