[360beast]

You may have been losing oil out of the turbo return seal that goes in the side of the block at the bottom, as that should have been renewed it might have been the source if your oil leak.

It might have also been leaking from the rocker cover at the back of the head and leaking down the back of the engine so you didn't see it, might have even been leaking at the front and going behind the cam covers so you didn't see it.

However if you were needing to top it up weekly I would have thought it would have been an obvious leak if it was high up so I'd say it is more likely to be the return seal.