Just in case anyone else has this bug u can
A. Put it on but never lock it as locking it is when it disappears and just putting it on is good enough for the game. (Though Riley or Bailey can't remember which loves to take keys)
B. Click on debug and there's three options cock vagina and futa, if you click on cock chastity cage will show up again.
C. Buy a cock from eclinic though I don't know you'd do this over option B unless it being a choice that doesn't bug/glitch out the game like debug tool could.
P.S. Using eclinic to buy a gender or debug tool automatically unlocks chastity.