MTGNexus

Saw an interesting situation come up in a game recently, and wanted to double check my rules knowledge.

• Player A casts Vanish into Memory on Player B's commander.
• Player B allows their commander to be exiled, and there is a delayed trigger to return it on Player A's next upkeep.
• On Player C's turn, they kill Player A.

Does Player B's commander ever return, or is it exiled forever?

For the record, we houseruled that it got sent to the command zone, but I believe that actual correct ruling is that it is exiled forever, since Player A never has another upkeep.

You're interpretation is correct. Nothing says you get to move it to the command zone later (the rule gives you one moment to move it at the instant to gets exiled to begin with) and then nothing brings it out of exile because the upkeep trigger never happens. Their commander is exiled for good.