Putting a lever there is like putting in a magic deck of cards.
Players have to pull the lever/draw the card(s). It's almost mandatory.
It's like a flash grenade that says Pick Me Up, you know they're going to.
Only way this could be more unfair is if it was a pressure trap or proximity trap.
Reminds me of my old Geometer. Glyph traps everywhere, and the DM ruled that my glyph-radar's range was less than the symbol's range, or that it was around the corner, out of sight, so I had to walk into the area to get to search for it. :\ so I never found any of them.
Until after they went off, of course.