The oil pretty much completely drained from my 850 while parked suddenly.
No oil leaks prior to this.

The oil leak occurred on the drivers side, under the air filter/battery area. The oil filter, oil pan, and drain plug were all clean with no oil coming from there.
Any ideas where the leak could be coming from based on the pictures attached? [see line/hose I have highlighted in red square]
It looks like oil was coming down from the hose/line shown in picture. The pictures were taken looking from the front of car towards the rear.

It's possible oil was leaking prior to parking and sprayed onto other areas.

Any insight/tips on what to check is greatly appreciated.

Notice the line I have highlighted.

Notice the line I have highlighted.

 

kind of hard for me to guess based on the pictures. From the transmission side of the engine (ie away from the timing belt) there's only a few places it can leak. The rear cam seals would be my first place to look. If you can remove the air box you'll be able to inspect the cam seals (remove the covers) and the distributor (it too should have an oil seal). I suppose its possible the oil could leak out from the head gasket but I don't think that's a high probability. next is to take off the head cover - there's a pcv tube that goes into the head under the cover and its possible its blowing oil onto the top of the engine and that's draining down the rear of the engine. With the air box off you should be able to look around at things like some of the PCV hoses which can also push oil out. If you see a mess, clean it up with some degreaser etc reassemble and recheck after a drive to see if that helps pinpoint the source.

 

I also vote rear cam seals. They are easy easy easy easy to replace. Amazingly easy.

They do take effect "suddenly" because they'll pop all the way out of the head.