Disappearing Topics

I have a project with about 300 topics. When my coworker logs-in from his computer he can see all of the topics. I am remoting into my computer using VPN and when I get into the project there are about only 40 topics-- they don't disappear from the project folder, but from the project.The topics are x-ed out on the TOC. We restored the project to an earlier version and it works when my cowoker gets in there, but when I do, the same problem happens.