I've had one vacuum pump come apart (the cam follower which is essentially a ball bearing---came apart). I have had no problems since replacing the pump and think I got all the old parts out.
On the other hand, an individual told me of a similar experience where a very small piece of metal (looked like a key from a shaft keyway---but very small) got past the filter screen on the oil pump, got into the pump gears and stopped the oil pump, with the result that no oil to engine---engine locked up and required rebuild. Just to be safe I believe that I would, at the very least, drop the lower section of the oil pan and make sure no small pieces were in the pan or up next to the oil pump screen trying to find a way past the screen.

__________________
K. Weimer
300SD (1)
300D (5) [Plus 1 parts]
300SEL 4.5 (2)
280SE (4)
280 (2)
250 (1)
250SE (1)
240D (7) [Plus 1 parts]
220D (11) [Plus 3 parts]
200D (2) [Plus 1 parts]
180c (with sunroof)

1995 Nissan UD1800 rollback
"If I can't fix it, it don't get fixed"