If your corporation has it limited who can delete, then the data should be retrievable from the unattached folder. It would be as simple as dragging the deleted information back into the perspective folders. In the event that your corporation allow anyone to delete, the data is gone and will have to be retrieved from the backups that you have at your disposal.
I would recommend having the backups restored to the DB and ALM repository utilizing a different project name and id.
1. Create a new project in Quality Center's Site Administrator
2. Have a DBA restore the backed up project into the new schema created by this new project.
3. Login to both the old and the new project in Quality Center in two separate Internet Explorer browsers
4. Copy and paste the items that were deleted from the newly restored project to the old project using the ''Copy'' and ''Paste'' options from the right-click menu List item
Once the project is restored, then it is as simple as dragging and dropping the tests and test sets into the respective places within the hierarchy of the project they previously resided in from the back up project. Unfortunately no way exists that would allow the run data to be retrieved, just the test set and and test data. Nothing within ALM currently allows for this to occur.