Trivia: The Star Trek: The Next Generation novel "A Herd Rain" was based on this episode. Picard and Crusher are pictured on the cover in the clothing they wore in the episode.
Trivia: As Troi talks to Picard about the language of the Harada, there's a model of the Enterprise-A behind her painted silver. The difference is that the nacelles are flat rather than in profile (straight up) to make it appear as a different ship.
Answer: Yes. The doors to the holodecks can be locked when in use by anyone aboard the Enterprise so they couldn't be disturbed. However, high ranking officers like Captain Picard could override the doors as it's seen that overrides are in use even for the crews quarters. Even Barclay, when he's indulging in one of his fantasies could have the doors to the holodeck unlocked by an override code.