gallery app deleted wrong pictures

This happened only once. I couldn't reproduce it. This is how it went:
I edited the second to last picture (rotate). Then I rotated the third to last picture. On both occasions, I didn't save the changes but reverted to original (I guess, cant verify, because the pictures are gone).
Then I deleted the last picture. After the delete dialog, this last picture was still shown. So I deleted it again. Still the picture was there. So I quit and returned to the picture browser. The two pictures (2nd and 3rd to last) were gone. I rebooted the phone, but they were gone.