Is it possible to search by SourceGUID
Yes, just search for the Guid using the search tool.
However, this may not find anything. The SourceGUID should already have been translated to its source name. If Alarm and Event messages are showing up with GUIDs in them it usually means the original source object is missing from the system.
As Rob wrote; if the alarm or event is presented with a GUID instead of name the object that it once was associated with has been removed from the system.
You can't search for something that does not exist.
I haven't tested, but potentially you can use the Locate... feature of the ImportExport tool to search for an object with that GUID in some backup (taken before the object was deleted). Launch ImportExport, select Locate... enter the GUID in the object name field (ensure object radio button is selected) and then browse to the backup you want to search in then click Search.
I assume you know that before deletion, you can easily jump from any alarm and event in the system by selecting a Structure Reference aspect from the context menu; eg by selecting the Control Structure aspect from an AC 800M hardware alarm's context menu you will be presented with an overlapping window containing a map where the hardware tree is zoomed in on the hardware that emitted the alarm.