why can i not find any Lights

[Sky]

don't be so hermetic.

The randart list is generated at the start of the game. There used to be an option to keep a randart list over multiple games, but it no longer exists.

Obviously, which artifact gets selected for a level is determined upon generating that level. You can have the same artifact generated multiple times, until you find it - walk on it or pick it up. Once you find the artifact, if you discard it, it's gone forever.

There is a game option to play with artifacts which are placed on a level only once - if you miss it, it's gone forever. As a payoff, you get a special symbol, "$" in the level feeling, to show you that an artifact exists on that level. (it's harder to play like this, believe me, i used this option for years)