I finished the game with 64 discs, but I can't find the missing disc... what am I supposed to do ? has it been patched ?

The Golden Phase disc is the one you're most likely missing. You have to clear Danger Zone all the way first, and on the first floor reset, you have to only clear the tiles that have the darkened glass beneath, like you're making a target. That will cause the Golden Phase disc to spawn.

Here's a picture of what I'm saying: https://imgur.com/a/9dn0q2J

It's the special Breaker in one of the ???? rooms (I think the WSW one). That is the extra 65th disc. (We could call it Hyper Breaker, going with the naming scheme for other upgraded discs maybe?)