Can't see all files on CD

You can try a program like ISOBuster (the free version should be sufficient) but frankly any time you start using multiple sessions or anything else with CD/DVDs these kinds of things become much more likely. You should also make sure to pull a copy of every file off that disc and either burn a new one or store them on some other kind of media, because at 10 years you're lucky you can read that CD at all. Burnable media generally doesn't last much longer than 10 years, even if stored in ideal conditions. Even some of the early commercially pressed music CDs are starting to fail now. Also, putting a label on a disc with an adhesive can cause discs to fail even earlier as the adhesive slowly makes its way through the tiny holes in the plastic of the disc and corrode the chemicals used to create the burnable surface. So if you ever wanted to know when you would possibly ever use knowledge of osmosis as a kid, you have your answer.