If all you did was change the directory for the domain in the control panel, the “old” directory the domain “was” using before the control panel change should have still been in your user area untouched.
If you accidentally deleted that directory, then you will need to find some “older” backups from before you made the change and the delete. *nix has no “undelete” safety net for dealing with such things; backups are your only recourse.
If there are no weekly.x directories in your .snapshot directory, I suggest you contact support and see if they can help. You may well be “out of luck”. While Dreamhost does try to keep backups of your stuff, it is your stuff, and at the end of the day it is your responsibility to keep it backed up (as is very clear from reading the DH TOS).
As a last resort, you might be fortunate enough to be able to recover a lot of your stuff from Google’s cache, or from the Internet Archive’s Way Back Machine - but that is a pretty ugly proposition.