Jack Knife - S7-E15
Revealing mistake: When Gibbs' car does the quick 180 to return to the gas station, It's not Fornell or Gibbs driving. (00:27:20)
Revealing mistake: At the end Gibbs puts the handcuffs on the bad guy and they walk off. However look carefully to see the bad guy is just holding the cuffs and they're not applied. (00:40:05)
Revealing mistake: When Ziva wakes up and has the sheet stuck to her face, Tony pulls it off. When he does you can see the glue patch on the page used to stick it to Ziva's face. (00:02:00)
Chosen answer: It is never stated, however she must have been there several years if she is on presidential detail.