The basic announcement is "Flight Attendants, Please prepare your doors for crosscheck" or something to that effect, said by the lead Purser prior to pushback or just after the seat belt is turned off upon arrival.

The FA then arms or disarms his or her door and checks the door across from them ("crosscheck").

If a slide is deployed, there are many consequences. First, those things go off with incredible force. If a food service person was opening the door, he could easily be thrown to the ground and injured.

Second, those things are expensive. The aircraft must be immediately taken out of service and a representative from the manufacurer (Boeing or Airbus) must be called in. This all costs lots of money. Third, both the FA whose door that was and the cross-checking FA all suffer penalties including relief of duty, fines, retraining, and if a repete offense, termination.

You saved the day, Dr. One Kay Lax!