Keycard combinations work like this:
![Image](http://s7.postimage.org/mfdam73cb/crappy_example.png)
So, even after the player has searched for 3 keycards, there's a chance things will not go as expected.
You could also try upgrading a single keycard by using the "Very Fine" setting. There's 1 out of 3 chances the keycard will upgrade 2 levels (Level 2 > Level 4). If you fail, you will get a Mastercard.
The Mastercard, however, can be reverted to a keycard with the "1:1" setting.
Download: http://www.mediafire.com/?1jxjjtmzd8gz9x6 (source included)