Alternator/Electric problem-TD4 Auto

I have an X Reg TD 4 Auto and unluckily I had some sort of oil leak which attacked the alternator last week and burnt it out, so she is laid up until a new unit is fitted later this week. A strange thing happened overnight, when I went to check the vehicle this morning, the rear tailgate window was opened. At first I thought the window had been smashed in but it was completely down. Does anyone have any ideas how that can happen, when the vehicle has not even been touched?

I believe the oil leak is oil been pushed up the dipstick tube and spilling out onto the alternator, possibly caused by blocked breather pipes somewhere on the top part of the engine. Has any had this sort of problem before?
Thanks

When connecting the battery the tailgate window drops automatically due to not knowing it's position. You need to press the buttom to put the window back up to the top and this recalibrates the window position.

Thanks for your reply.