Look in your AdminCP logs of vBulletin for AdminCP/ModCP access to make sure there wasen't a member w/ access that removed the data.
- Cpanel / Vdeck
Download log files. This way we can get a time frame when those files were last "viewed" ect ..
Once you know the last "time/date" the files were on the server.
- help to look @ cron job running @ the same time ect ..