"I thought we'd go unscathed" = 我还以为我们能够逃过一劫(没受损失or损伤)
"以为" usually means “thought”, but the truth turns out to be the opposite.
"认为" means "think".
other ways of saying "thought" is 曾认为 or 曾经认为, sometimes we just left out "曾经" for convenience. 曾/曾经 = used to