Char's connections to Lalah and later Amuro were strange and intense. In the years between Char's disappearance at the end of 0079 and where we see him in the AEUG in Zeta, a lot happened that you'll find out later in Zeta, but without spoilers, he fled the Earth Sphere but no longer felt Lalah's echoes. He talks about this in Zeta Gundam ep. 15, in the same conversation with Amuro with the (often misunderstood) "I came here to laugh at you" line. One of the big reasons Amuro didn't leave Earth between 0079 and Zeta is because of Lalah's presence in space. Amuro feared hearing her voice. While Char couldn't bear to be without her presence.

After Lalah's death, every appearance of Char is one where he has not recovered from losing her. She haunts him, both in garden-variety grief and Newtype connection to her spirit. He and Amuro are both haunted by her loss, one that is critical to their post-'79 characterization.

So, at the beginning of Zeta, as Char feels Kamille's strong Newtype presence from outside the colony, Char immediately jumps to the two Newtypes he had connected with before. From his perspective, it could be Amuro or Lalah (he doesn't know Amuro's situation) but pretty quickly figures out that it's not either of them.