I am very well aware the gaskets only fit one way round - still doesn't stop them from being fitted incorrectly - and by incorrectly I don't necessarily mean the wrong way round.
I trust you applied the required and correct sealant to the specified areas, fitted the two gaskets, used new sealing washers on the bolts for the cover and tightened them down to the correct torque in the correct sequence to prevent warping of the cover and to seat the seal correctly.