no one can actually tell, but if you've been ah... 'roughly handled' by the person who fingered u (in my case he didnt have a clue what to do and so he hurt me a bit and made me bleed) then perhaps any injuries may point towards fingering as a possible cause. But yeah, even then i think it would be hard to tell.
'May no one ever come to you without going away better and happier. Everyone should see kindness in your face, in your eyes, in your smile.'
Actually, I took the time to research it, and a doctor can tell if a girl has been fingered. It is more of a phycological way (like if the girl has been molested). They might tend to act strange during a physical. Hopes this help you out.