The fact Peter is basically living like an Observer hasn't entirely escaped him, and he knows he'd get a much different reaction from a human. Say, Olivia, for instance. He watches the Observer for a few moments, assuring himself he's likely not going anywhere, and then pulls out his phone.

Looks like Astrid gave him a call last. Peter lets out a breath he didn't know he was holding, glances at the Observer again just to be sure he hasn't moved, and listens to the message.