Getting Data Back after Wrong Data Restore in SQL Server
The database has log and data files that are stored on the file system. If the sys admin has a process of regularly backing up the location where the database files are stored then you might be able to get some of the data back. Assuming that you can get these files from before you overwrote them - then create a new database and attach the db and log file to it. You will most likely still have some problems but you might get some data back.