back on our feet
"Do you think he's a pro?"
She shook her head. "He acts like someone who's making it up as he goes."
"If he didn't take the casing, someone else did. Delacorte, or one of his deputies."
"We don't know that."
"But we think it, don't we?"
She didn't say anything for a while.We were back on our feet, looking down at the wind-blown grass.
what does"but we think it" and "back on our feet" mean?