Is it possible to go back in time to retrieve a Visio drawing and compare it with its current version to see changes that were made?
Each time configurational changes are done on the system, a record will be offloaded in the Recycle bin folder. So in there you can find your recent changes and manually revert or compare. See DataMiner Help: Recycle Bin
It is possible, but you'll need a flux capacitor, some plutonium and a fast car.
All jokes aside, Thijs is correct indeed.
In case the visio is attached to a view or service, and the new visio file has a different name, then you will also still find the old file in the views folder.
For protocol visio files this is not possible. Then you'll need to rely on the recycle bin.