They ejected. Ditching a B-1 wouldn't be fun.
Each B-1B crewmember has an ejection seat. Given the choice between punching out and ditching, I'd punch out. Ditching is tricky under the best of circumstances. Ditching a plane like the B-1 wouldn't be easy with those big engine pods beneath the plane. I suspect they'd cause the plane's nose to dig in on impact with the water. In addition, I'm pretty sure it was dark over there when the plane went down. Attempting to ditch any plane at night is close to committing suicide.