The DreamHost backups are really “Snapshots” by NetApp. It basically does a “diff” of what’s changed since the last snapshot. If nothing’s changed, a snapshot takes up no space. If only 100 Megs of files have changed, then the snapshot is only 100 Megs.
So it’s more like a differential. The snapshots occur on an hourly, nightly, and weekly basis. Hourly is since the last hour. Nightly is since the last nightly, and weekly is since the last weekly.
This is just from my memory from some NetApps I used a few years ago. So if you put 10 megs of files on, then delete an hour later, and then wait 5 hours, the Hourly snapshot with those files is gone. Unless you’re lucky enough that the Nightly caught it, in which case it’ll stick around for about 2 nights.
In other words, if you wait too long to do a restore, it may be too late.