If you have a disaster, and you need to restore to some point in time prior to the last log backup you have, what’s the first thing you should do at this point in time?
Make a full backup, of course.
Actually anytime you complete a restore sequence, you want to do a full backup immediately before you turn users loose to do work. Why is that?
Think about what happens if you complete the restore and then have another issue? You would have to go through the entire restore sequence again from before the first disaster. If that were a full backup, a differential, and a dozen log backups, would you want to explain that delay to your boss again?
Would you even want to go through it?
I wouldn’t, and it’s easy to prevent. Once you get done with your restore, start a full backup right away. You might never need it, but then again, you probably said that about the full backup you just restored.