SharePoint does not provide a handy way to administrators to conveniently recover a deleted site or site collection. SharePoint in versions 2007 onwards, Recycle Bin supports recovery of list items and entire list. In case SharePoint site disappear or mistakenly deleted, the solution is for restoring site collection from backup of database.
There are two methods to Retrieve Erased SharePoint Sites
Suppose you have not updated site collection backup but you have backup data and you wanted to recover deleted site collection by using SQL server backup by using following given steps:
Drawbacks to Restore Missing SharePoint Sites method
This method has no surety to work, if it is the case of severe corruption. It is better not to use this and look for some other solution. To run steps is not an easy task unless and until you are well-versed with technical skills. If you miss any of the steps in between, you need to follow the entire processing again.
If you are thinking to use SQL Server backup solution then also you will not going to get absolute results. So, why not go for some simple solution rather. The easiest solution is resided in professional SharePoint recovery tool.