Power Steering on 2004 BMW 325i

My wife drove 2004 325i to store, no problem, got in to leave and no power steering. Has fluid, no leaks and the belt is on and pump spinning. What happened?

Asked by for the 2004 BMW 325i
I have no personal experience of this but see a Technical Service Bulletin from BMW concerning loss of steering assist/heavy steering effort required (SI B 32 19 05)
It attributes internal pump wear to power steering fluid impurities and says to replace the pump and fully flush the steering hydraulics.
It is best not to jump to conclusions but have the system checked out by someone familiar with BMW and be aware of this TSB.