I checked the oil level today and it was almost empty.
Last time that I checked the oil level was about 3 weeks ago and it was almost full.
I did work the bike rather hard in the last couple of days. I rode more than 800 Km in three days, including a nice day offroad and high speed motorway riding.
Anyone else encountered this?
I was told that big bore singles use oil, but this seems too much. Especially when considering the fact that the bike is on the road for less than a year.

On a different subject:
After a water-crossing that I did, I drained the airbox oil tube (it was full all the way up). To my surprise, after the oil water came out.
Today I removed the air filter and looked inside the airbox. There was some residual water on the left side of the box.
I reckon that most of the water that got in the box, went into the lowest part of it (i.e the connection to the drain pipe, which is rather deep).
The bike runs as usual. No new sounds or behaviors.
So my questions are:
1) What are the chances that I caused major damage?
2) How can I tell if there's water in the system?