Why can't I remember *this* dream?

Today I had a really frustrating dream, and for some reason I can only remember the end of it.

For some reason I was on an aeroplane, and something was wrong with the plane so it was diverted to land on a ship (?) but when we got to the ship the ship sank and then we got diverted back to the airport. One of the DCs said “Don’t you think it’s funny how…” and then proceeded to give a summary of everything that had happened so far in my dream.

When I woke up I could remember the end of the dream (it involved accidentally drinking sewage and I woke up trying to spit over the side of the bed - who wouldn’t remember that?) and I started to work through it backwards. I got back as far as the DC telling me the summary of everything that had happened, but I can’t remember for the life of me what he said! I’m sure he said the original reason that we were in the plane in the first place.

This is really frustrating - I was even told what happened but I couldn’t remember that one bit of the dream. Has this ever happened to you?

Yes on many occasions when an LD is pretty much a blur or when I remember having a whole dream but I can only recall an image or very minor detail.