it's extremely common to not have any stones come out. Just try again in a few weeks. The next time, though, you might want to consider taking magnesium citrate the morning after you drink your oil; it's a rather mild laxative but very effective. You can get it at any drug or grocery store in the laxative section.
Don't worry...this is very common. About 1/2 of first time flushers don't produce stones.