I just played
Sphinx of Lost Truths without kicker, tapping out at 5 mana. After it entered the battlefield the animation of it's ability (draw 3 cards, discard 3) played, but nothing happened - no draw, no discard.
Edit: Here's what appeared in SCRIPT_LOG.TXT after the game
[lua] [string "SPHINX_OF_LOST_TRUTHS_99185751_TITLE (RESOLUTION_TIME_ACTION)~0x00000a31"]:2: attempt to call global 'GXSC_Draw' (a nil value)
[lua] [string "SPHINX_OF_LOST_TRUTHS_99185751_TITLE (RESOLUTION_TIME_ACTION)~0x00000a32"]:2: attempt to call global 'GXSC_Discard' (a nil value)
[lua] [string "SPHINX_OF_LOST_TRUTHS_99185751_TITLE (RESOLUTION_TIME_ACTION)~0x00000a31"]:2: attempt to call global 'GXSC_Draw' (a nil value)
[lua] [string "SPHINX_OF_LOST_TRUTHS_99185751_TITLE (RESOLUTION_TIME_ACTION)~0x00000a32"]:2: attempt to call global 'GXSC_Discard' (a nil value)
[lua] [string "SPHINX_OF_LOST_TRUTHS_99185751_TITLE (RESOLUTION_TIME_ACTION)~0x00000a31"]:2: attempt to call global 'GXSC_Draw' (a nil value)
[lua] [string "SPHINX_OF_LOST_TRUTHS_99185751_TITLE (RESOLUTION_TIME_ACTION)~0x00000a32"]:2: attempt to call global 'GXSC_Discard' (a nil value)