What would cause the following behavior on an Ubuntu 12.04 system?

1. I've SSHed into a machine as the "ubuntu" user.
2. Running ls -lah /data/* shows dozens of non-empty files (e.g. file1.txt, file2.txt, etc), all owned by the "ubuntu" user/group, and with full read/write access.
3. If I try to cat /data/file1.txt, bash gives me the error "cat: /data/file1.txt: No such file or directory"

In short, ls is listing files, but in every other way, the files essentially don't exist. I can't cat them or read them in any way. Even giving all the files 777 permission doesn't change anything. This is really bizarre. What's going on here?