Check Engine light was reset?

I just purchased this my toyota celica yesterday, after checking the oil i did not place the dipstick back into the proper position. It wasnt pushed in all the way. After driving the car for about 2 days, and taking it on a 100mile trip i noticed the check engine light was on. Therefore right away i was trying to trouble shoot for things such as a loose gas cap, and i came across my dipstick. I pushed it in all the way and resetted the check engine light by pulling the battery. Than i took the vechicle for a drive for about an hour. My question is now long does it actually take for the car to notice something is wrong?