Restoring the site collection once it gets deleted inadvertently.
You need the full URL of the site collection which you want to restore back to start.
Step1 : For Example, I have a root level site collection having full URL as "http://<<host name>>:10000".
You can execute Get-SPSite cmdlet to get the site object.
$mysite = Get-SPSite http://<<host name>>:10000
Step2: You can print the GUID of that site by using "id" property of that object in last step.
PS C:\Users> $mysite.id
Guid
----
7044efc1-786f-493b-b3d5-0056add40bb9
----
7044efc1-786f-493b-b3d5-0056add40bb9
Step 3: Then you can use "Get-SpDeletedSite" cmdlet with the id as a parameter to confirm the other details of that site collection such as path and deletion time.
PS C:\Users\> Get-SPDeletedSite $mysite.id
WebApplicationId : 740953c9-7041-4130-994a-7d85864975d3
DatabaseId : 78e0f455-c59d-4404-83c7-085309762fdc
SiteSubscriptionId : 00000000-0000-0000-0000-000000000000
SiteId : 7044efc1-786f-493b-b3d5-0056add40bb9
Path : /
DeletionTime : 1/26/2016 9:40:22 PM
DatabaseId : 78e0f455-c59d-4404-83c7-085309762fdc
SiteSubscriptionId : 00000000-0000-0000-0000-000000000000
SiteId : 7044efc1-786f-493b-b3d5-0056add40bb9
Path : /
DeletionTime : 1/26/2016 9:40:22 PM
Step 4: Last step is to run "Restore-SPDeletedSite" cmdlet with the "-Identity" parameter. You have to pass on the same id or GUID which you got in last steps. Press 'Y' for confirmation.
PS C:\Users> Restore-SPDeletedSite -Identity $mysite.id
Confirm
Are you sure you want to perform this action?
Performing operation "Restore-SPDeletedSite" on Target "/".
[Y] Yes [A] Yes to All [N] No [L] No to All [S] Suspend [?] Help
(default is "Y"):Y
Are you sure you want to perform this action?
Performing operation "Restore-SPDeletedSite" on Target "/".
[Y] Yes [A] Yes to All [N] No [L] No to All [S] Suspend [?] Help
(default is "Y"):Y
After execution of step4, your site collection would get restored back.