uploaded files are not displayed on the front end

I have a library items (pdfs) displayed on the webpage: www.annapolis.gov/.../minutes

They are displayed by library - category - tag. All the documents work - they show up on the page, except those that are tagged by 2011. I can't download them, I can't view them, I can't display them. All of them used to work before today. The error I'm getting is this: 

Server Error in '/' Application.Could not find file 'C:\inetpub\wwwroot\Annapolis\App_Data\Storage\FileSystem\0dfa672e-e536-45ee-bf5c-641b35b7032e'.Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.IO.FileNotFoundException: Could not find file 'C:\inetpub\wwwroot\Annapolis\App_Data\Storage\FileSystem\0dfa672e-e536-45ee-bf5c-641b35b7032e'.

Source Error: 

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.
Stack Trace: 

[FileNotFoundException: Could not find file 'C:\inetpub\wwwroot\Annapolis\App_Data\Storage\FileSystem\0dfa672e-e536-45ee-bf5c-641b35b7032e'.]
DynamicModule.ns.Wrapped_OpenAccessLibrariesProvider_251f57e34abe4d81836aa2ff7823089b.Download(IBlobContent item) +202
Telerik.Sitefinity.Modules.Libraries.LibrariesManager.Download(IBlobContent item) +28
Telerik.Sitefinity.Modules.Libraries.Web.LibraryHttpHandler.GetMediaStream(LibrariesManager manager, IBlobContent content, Int32 size, Int64& streamSize, Int32& bufferSize) +670
Telerik.Sitefinity.Modules.Libraries.Web.LibraryHttpHandler.GetMediaStream(LibrariesManager manager, MediaContent content, Int32 size, Int64& streamSize, Int32& bufferSize) +22
Telerik.Sitefinity.Modules.Libraries.Web.LibraryHttpHandler.SetResponseOrCacheData(HttpRequestBase request, MediaContent content, LibrariesManager manager, HttpResponseBase response, OutputItem outputItem) +2768
Telerik.Sitefinity.Modules.Libraries.Web.LibraryHttpHandler.PopulateOutputItem(HttpRequestBase request, MediaContent content, LibrariesManager manager, OutputItem outputItem) +49
Telerik.Sitefinity.Modules.Libraries.Web.LibraryHttpHandler.GetOutputItem(HttpRequestBase request, HttpResponseBase response, ICacheManager cache, String key, MediaContent& content) +716
Telerik.Sitefinity.Modules.Libraries.Web.LibraryHttpHandler.ProcessRequest(HttpContextBase context) +545
Telerik.Sitefinity.Modules.Libraries.Web.LibraryHttpHandler.ProcessRequest(HttpContext context) +42
System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +341
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +69

Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.34212

How do I fix it?

Thank you!

It's looking for that file on the file system and can't find it...if you browse on the server to that folder, can you see "\App_Data\Storage\FileSystem\0dfa672e-e536-45ee-bf5c-641b35b7032e"?

Steve, no, the file(s)  with those references do not show in the file system. And I don't understand what had happened because all of them were there (on the front page, thus, in the backend as well) for years!

So, when I go to the "Revision History" link and revert to the previous version, I at lease can view it. But, when I try to publish the reverted version, it's not showing up. So, for each file, I have to go to the previous version, download the file, delete the old one then upload the one I downloaded. I need to find out why it happened, how to  prevent it from happening again, and if there is a less tedious and time-consuming way to fix what's broken now.

Any  help is greatly appreciated! Thank you again!