Hi, I'm Pete. Welcome to JustAnswer! I'm reviewing your question now, and will post back with your reply ASAP.
To get back missing lines you need to have another staff on the score which does have barlines (if you don't have one then press 'i' for instruments and add one).
Then on the new staff click at the point where the barline meets the staff and you will again get a little blue box at that point.
Drag this blue box towards the staff that is missing its barlines and they will re-appear and also be attached to the new staff.Then either delete the new staff or drag the little blue box back towards the new staff which will then stop the barlines being joined between instruments.
Let me know if that works?