^Do you mean before Crusher is abducted? She specifically tells them not to beam her up because she's doing precarious work.
If you mean after the abduction, Data says that they cannot locate Crusher. He theorizes that either her communicator is deactivated or she's being held somewhere that is shielded from their scanners.
If you mean after the abduction, Data says that they cannot locate Crusher. He theorizes that either her communicator is deactivated or she's being held somewhere that is shielded from their scanners.