Helaman 5:21

And it came to pass that they were taken by an army of the Lamanites, and cast into prison; yea, even in that same prison in which Ammon and his brethren were cast by the servants of Limhi.

They were caught by a Lamanite army and thrown into prison. It was the same prison where Ammon and his brothers were put by Limhi’s servants.

A Lamanite army captured them and threw them in prison—the same prison where Ammon and his brothers had been held by the servants of Limhi.