Problem with references with TFS

Hi!

I use TFS and when i checked out the whole project today, i see a lot of, 

Error CS0234 The type or namespace name 'Storage' does not exist in the namespace 'Microsoft.WindowsAzure' (are you missing an assembly reference?) 

In the project file i see this:

<Reference Include="Microsoft.WindowsAzure.Storage, Version=6.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35, processorArchitecture=MSIL"><HintPath>..\packages\WindowsAzure.Storage.6.0.0\lib\net40\Microsoft.WindowsAzure.Storage.dll</HintPath><Private>True</Private></Reference>

But when i go to this folder, there is no dll file, only a xml file. On my other PC, where i checked in this code, there is a dll file. Why is this dll not checked in with TFS?