Found a tute on fusible thread:
http://www.byannie.com/fusible_thread_video_1/

It looks like it is temporary, for example to anchor something until you sew it?

I should show the whole quilt. I am wondering about ruining the design by applique with another piece.

The loose seam is in the blue right of the middle flower.

I would just use a very small ladder stitch so it would not show.

It would be a bug, butterfly or friendly worm applique for me if it were my quilt. Good luck repairing. Those errors are always so sad.

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.

You could use "Liquid Stitch" made by Dritz. Glue the piece in place, then iron with a dry iron to dry the glue. This type of glue is permanent and is very soft and pliable. If you used some other glue on it, check the bottle, it may be washable glue which means when washed the glue will wash out and leave you with a hole again.

I'm using Liquid Stitch on appliques and it is working beautifully. You can buy the little needle tip applicators to fit the top of the glue bottle, I found mine in the model car paint and glue section at Hobby Lobby.

Is the Dritz Stitch Witchery I already used not permanent?

I used the Dritz Stitch Withchery under the open seam, folded it under and used it again, so I assume I glued that to the batting or something. Then I used slip stich with invisible thread, that was hard to see! LOL that's funny, hard to see the invisible.

Anyhow. It worked, except I wish I had asked for advice before I glued the top inch (the part I initally thought was loose).

I use liquid stitch , its not hard and stiff, also it don't wash out , so far ..

The Stitch Witchery worked. In fact, I had to use it for another part where I was snipping threads and accidentally cut the backing fabric.

This quilt is almost done. I stitched around the flowers, using walking foot, the lines are octogon.

I top stitched the pieced pieces with different built in choices of Janome. I used warm and natural and measured, so the parts I stitched are less than 10". So I am not going to FMQ the background like I was thinkng of doing.