Kathy - I found your message intriguing.  I have twins. If both babies are
close to you then you feel comfortable.  But if you're *with* only one baby,
you're often thinking about or watching the *other* baby (you have to take
care of them both and you know the one that's with you is O K, but you
"miss" the other one - does this make sense?)  I even feel like this when
I'm seeing clients with twins, continually checking that the other baby is
still alright!  That's one explanation.

The other might be that from a survival point of view mothers and babies are
meant to sleep in close body contact.  When your client wakes up in the
middle of the night and the baby is not there right next to her, quite
naturally her first instinct is panic, the baby should be there, but he is
not - where is he? She becomes frantic.  I wouldn't call this kind of panic
a hallucination, it seems more like a normal natural instinct!  Maybe she
should sleep with both babies in the bed, and everyone would sleep more
peacefully.
Pamela, Zimbabwe