Continuity mistake: When she sees the little boy's ghost, Gwen's hair alternates repeatedly between neatly-combed and windblown/messy, depending on the shot. (00:03:30)
Revealing mistake: From the first "front on" view of Gwen and Owen in the arcade as they are running to catch the alien device, you can see behind Gwen to the right that Owen is being played by a stunt double.
Answer: Several times during the episode, most notably at the beginning when the old grave is discovered, Tosh holds a devise that looks a great deal like the Sonic Screwdriver that she uses to determine the age of the skeleton. However, a search of Google images shows that it is not the same thing.
OneHappyHusky