Holy...okay I just realized something. In Volume 38 Round 414 we see Sird about to battle Riley. That's the last time we see her as of now. Riley appears in future rounds so we know he didn't lose (or at least he wasn't killed or severely injured). So...what if...Sird actually LOST the battle (that actually wouldn't be surprising since her injured leg sets her at a disadvantage) and she was either arrested or "eliminated"? We don't see her with the other commanders in Platinum so if she was loyal to Cyrus, then this could be a plausible explanation. I would have realized this a lot sooner but it said on Bulbapedia that Sird escaped, which made me (and apparently a lot of us) assume that Sird is still off somewhere waiting to make another appearance years later, potentially extremely random this time.