Okay, so it probably wasn't in any danger of falling off the engine, but apparently a couple of the retaining bolts that hold it on broke, and it was kind of left dangling there.

The engine was replaced a few weeks ago and this past weekend I started hearing a rattling/ticking/clicking sound from the engine bay. When I hit the A/C yesterday, a belt started squealing loudly, I smelled burning rubber and I then found the compressor wiggling around with the drive belt about to come off. It was dark when all this happened, so I couldn't work on it at that time. But since it was the dealer's fault anyway, the car went back this morning so they could fix it. So yeah, the service manager called me earlier today to tell me the bolts had snapped off. He wasn't clear if they all broke, but I don't think I would have been able to move it around that much if even one bolt was secure.

So, the lesson for today: follow torque specs!

Oh, and there was a small coolant leak they're fixing too. Hopefully this will be the last time I need to take it back to the shop, as a result of the motor replacement.