"Mushroom farm" room?

[King Kull]

Player from the 90s (!) returning for another go... finding it to be a much richer game now, and overall a very good experience.

A question: I triggered a high item level feeling at 1500'. Of course, I was hoping for my first artifact. Instead, there were very few items, none of which were good. The only oddity was a room that had mushrooms in neat little lines on the floor. Is that what triggered the LF? Was quite a disappointment - if the mushroom farm was the source, perhaps that impact on the LF could be toned down in the future?

[DavidMedley]

Maybe you have an un identified scroll or potion. It's not the mushroom room.

[Sky]

*remove curse*, rune of protection, that stuff can give you a high level feeling, as can things like mithril plate armor - which you may have ignored if it was, for example, [60, +0].
if you reeeeally can't find anything, use the 'K' command to temporarily unignore items.

[Sphara]

Any missing high-tier (and possibly unreadable) books on the floor?

Those are notorious for triggering high LF and are easy to miss, if you just returned to the game after >20 years hiatus.