Sven
We may have been at cross-purposes here, I thought you were referring to the Oil Filter inspection (if there is one?) but perhaps you were referring to the feet cracking inspection? If so, these are specific inspections of the specific parts, the latter not being related to loss of oil (rather to loss of the entire MGB), and of course the best way to notice a problem is to see oil all over the side of the helicopter after landing. So really the point is, can such a fault develop so as to lose all the oil during the course of 1 flight. Clearly with the oil filter the answer was yes, but as to other possible causes we can't be sure but perhaps its unwise to rule it out.
HC