C4R GUID.rvt Collaboration Cache
Autodesk has changed the path and the way local copies of files are stored on your computer. It used to be that a Revit user goes to the Revit Options>File Locations>C:\Users\rsidawi\Documents. This is no longer the case. Refer to the following articles that explain how the local files are stored on your computer.
Collaboration for Revit: Finding local copies of files
An Outage Affects Collaboration for Revit
https://help.autodesk.com/view/RVT/2018/ENU/?guid=GUID-0E4165D7-B7BA-4334-A5BA-B1B04BBFF4CD