Saw this question on the Ask a Judge IRC.
Alison casts
Silumgar's Command choosing the second and third modes and targeting an artifact for the bounce and
Rusted Relic for the creature.
The bounced artifact drops the number of artifacts controlled by Alison's opponent to below 3 and Rusted Relic is no longer a creature.
Is the -3/-3 effect placed on the noncreature Relic, but it just has no effect while Relic isn't a creature, similar to a +1/+1 counter sitting on
Llanowar Reborn?