The problem here is that somehow Premiere is unable to find the indexed files on the next load in. Either someone is deleting them, or that directory changes location somehow (That can happen with networked drives).
I don’t know much about HDD Sheriff, but it could be imposing a quota on the drive, or deleting those files afterwards if they go beyond a certin size, which would make sense on a public computer.
It is verly likely the issue here.
Vince