General Maintenance & Repairs - Low oil light, 1-1 1/2 quarts missing

I went on a long trip...i'm due for my usual 3000 Mobil 1 oil change now. 300 miles before I was due my low oil light came on so I checked my oil levels after 5 mins of cooling and then again after thirty mins of cool down. The oil level was VERY far below the acceptable level. I picked up 2 quarts of oil and ended up putting in 1 1/2 quarts. The oil level ended up being almost in the middle of the acceptable run level. I didn't do the full oil change since I was 240 miles from home so I will do it soon. My car isn't smoking nor is it leaking oil on the driveway. Anyone have some ideas on what could be causing this?

You already mentioned the only 2 options, burning or leaking. It doesn't evaporate. If you don't see any leaks, that leaves one option. That's not a lot of oil over 3000 miles, but obviously you need to check it a bit more often.