X5 - oil pump damage

I have a 2005 X5 that I bought used from a private seller about a year ago. I brought it to the dealer for an oil change and to check some warning lights and they told me "pieces of the oil pump broke off during the oil change" and the oil pump needs to be replaced. Everything I could find says the oil pump should last the life of the engine. Even my service rep says it's really unheard of. It's out of warranty and I just have to eat it at this point, but I'm curious if anyone has a suggestion for why this may have happened. Is this a problem others have had? Also, someone suggested I write to BMW to try to plea for warranty reprieve because it's so out of the ordinary. Thoughts?