The drone is set to activate as soon as it detects Magnus's or Galahad's voice raised on the word SecUnit. (Because Murderbot knew they were never going to remember whatever secret code they came up with when they actually needed it.) It does so now. It pings SecUnit, and also makes a literal ping! noise as it emerges from the foliage.

"Copy," says the tinny little voice. Then it says, with considerably more SecUnit-like inflection, "What the fuck happened?"

(In the Mansion it's already on its way to Nina's room, at slightly less than top speed, which is still really fucking fast. Simultaneously it tells the nearest drone to notify Galahad as well, having learned its lesson the last time.)