[It was possible Sora had wandered off, but she definitely figured one of them would have run into him already, with how much they were thinking about him. She doesn't want to think the reasons for him not being there are bad, but can't help it at least a little...]

I'm not entire sure on the 'how' part, either...but a lot of us at least share some memories with Sora because we were fighting with him, right? So, maybe since this is his heart, we can jump from a memory we share with him to one that we don't, if they go from one to another anyway.

It's something we can try, at least. [She definitely hoped it wouldn't require Sora's presence with them to find his own memories.]