If it's a lie, that does raise plenty of other questions, but if it's truth -

They're missing a chunk of time, they don't remember how they got here. Something has to have happened in there, and that something, Hijikata's sure, is going to be what they need to figure out how to clean house here and move on.

"I get the feeling going out there is a one way trip."

Which won't necessarily stop them from making it, but it does mean that maybe another look around the morgue is in order, first.