Sometimes, during the process of making art, the transferred drawing can get lost. I have a few things I do to combat this or to fix any issues.
You can make marks on your paper to realign your drawing if things go awry and/or you can tape the paper to the side of the watercolor paper and leave it taped there until after you do the first few layers.
This is my transferred drawing, you can see on the right that the paper is still attached and can be folded behind the watercolor paper when I go to work. You can also see the triangle marks on the left.
I also have a way to re-transfer when my lines are hard to see in some areas. In the case here I could no longer see the leaf on the left and a few other areas.
I cut out some of the background paper around some of the shapes in the drawing and re-taped and re-transferred. It's not perfect, but it works well. I need to do this at times on my pieces.