Im not sure what has happened but it is always best to actually
copy and paste in these instances.
The "move to " may loosely mean
"cut and paste" in which case you end up having the card empty
As an aside too, it is best to always format your card with the camera
I recall once having a "rouge " card reader too. Once I used it, the camera would then not see anything on it again unless I formatted it.. fortunately I had 2 card readers and the second on confirmed that the images were still there.needless to say I binned the offending card reader..This was with Smart media cards though ( I think they've gone the way of the Dodo

)