All will become clear, trust me.

Besides, think about this: They had a whole wide world to hide Xander in, and that's a lot of ground to cover, no matter how many people/demons you've got looking.

The plan itself was solid (and yes, there was a contingency to get Xander out very fast, but things went really bad off stage where Alex can't see it), it's just there are several things that were totally out of their control that went horribly wrong.

As for Xander...well, wait and see...