Yesterday I reached 50th level of CoC with monk/barbarian troll, but no gates were generated (there wasn't also any message indicating that I reached the level with gates, but I don't know, if any message should be generated). I was wearing amulet of elemental fire the moment I entered the level. Dug almosl all the level searching for secret doors or rooms. The screenshot shows all the level (it is rather small). The pile of items near the staircase is a pile of stones left after digging.
As I said in the forums, if the level was of "small" type, the gates could have been generated below your character outside the level range. Missing a y-axis check?
Fixed for ADOM II 0.2.4. Please send your real name to creator(at)ancientdomainsofmystery.com for it to be included in the credits. (If you were already asked to do so you can ignore this message. Please include a reference to the bug or RFE you are credited for.)