2005Ford Focus 1800 tdci

Customer booked in for mot and service but car would not start,AA bring it in on truck as they could not get it started and said its fuel pressure fault,that was yesterday,too busy with tests yesterday so left it until today,(yes sunday)

Went in today,checked fuel in tank that's OK.
Checked for fault codes found none and nowt there to starve the engine of air.
Battery was a bit flat.
Checked for fuel at pump none,checked for fuel at filter not much there so its deff fuel supply fault.
Anyway bled it through system with mityvac,the engine started and seems ok.

So,
i ended up with no fault codes,customer says vehicle did not run out of fuel,no leaks on the fuel system,it ran ok until it would not start sat morning
It seems at this stage that all it needed was bleeding through.

Anyone come across this problem as my findings where inconclusive to the cause.