How do I fix a site after I removed a module? I deleted a module without disabling and uninstalling it first.  Now I just get a blank white screen, but I don't see any error messages.  What can I try to fix this?
Run the following query. 

select info from system where name = 'module_name';


You will get a blob. Within this blob look out for text after version. You can find the version of the module here.

Download this version of the module. Place it in sites/all/modules folder(you can also find out the previous location from the file-name field in system table), uninstall the module. Now delete the module.