Oil drainplugs shouldn't fall out right?

[Val]

My bike is just over a year old (2007 Model, new out of the box in 2008). I took it in for its 1000 km service last year then 2 weeks ago at 6000 km. I've never had a problem with it.

After riding about 300 km after the oil change, the oil drain plug fell out and the bike started dripping oil. I was about 1/2 km before a nearly 90 degree curve. Not knowing I was driving on an oily tire, I slowed and started through the curve and needless to say the bike did a nice 3 point slide on the left handlebar, footpeg and rear turn indicator. I continued onto the gravel shoulder. I stood up right away, hubby came back, neighbourhood residents came out. No more damage on me than on the bike. Hubby followed the oil drippings back to where they started and retrieved the oil plug from the side of the road, replaced it, tightened it, filled it up again thanks to a resident and cleaned off the back tire with cleaner, and we continued on to lunch.

Next day I talked to the shop owner, who said that his mechanic couldn't have left it untightened because all of the oil would have been pushed out right away due to the extreme pressure. ?So I rode it for that long and it spontaneously loosenned and popped out?

Any ideas? :??: Can something else have caused this, other than the plug not having been tightened properly after the oil change. (I don't have enemies, and my kids and hubby are NOT after the insurance money, so I don't think it was sabbotaged.)

Thanks