Try
http://www.psul4all.free-online.co.uk/intro.htmGives a complete summary of Ghost Trains and trains taking unusual routes in 2012 it also has historical records.
Not sure what constitutes a ghost train rather than booked service over an unusual route.
I suppose the classic Stockport Staybridge one way on a Friday counts as ghost train but the line is apprently also used by the Rail Touring Co Scarborough Flyer!
But what about
Bristol Dr.Days Junction - Feeder Bridge Junction (123,132) PC01
1553 SSuX Bristol Parkway - Bath Spa
Also used by trains (diverted from the direct Swindon - Bristol Parkway route) shown to call at Bristol Parkway with extended station time (or Bath Spa then Newport), but not shown to call at Bristol Temple Meads: none shown in timetable.
To quote a
FGW▸ example.
Editted to elimate some typos and introduce others. I realyy must learn to proof read!