It happens, especially with modern releases or with players who have tons of cards. However, I second C2Cigars tip about filtering by card number. That is, without a doubt, one of the best search features on this website. Sometimes, I'll use it even when I know what I have, just to get to the card quicker.
Highly, highly recommended function that is a time-saver, and super helpful. Welcome to the Database!
I'll never quit collecting entirely, but I am downsizing. Check out my COMC store and help me thin out what I don't want so I can buy cards that I do want. See something you like? Send me a message on here, and we can knock the price down quite a bit. I'll even take a bit of a loss if it means getting you a card you really want.