Is being arrested for 12 hours for a bench warrant considered being imprisoned?

I ask because I just received a job offer and on the form I have to fill out there is a question asking if I've ever been "imprisoned"? Four years ago I missed a traffic violation court date because I got the times mixed up and couldn't leave work. I received the bench warrant a couple of weeks later and went to the police station believing that I could just pay a $70 ticket and go home. They arrested me and sent me to the county jail but released me the next morning and the ticket was actually thrown out because the officer that issued me the ticket didnt show! I checked my records a few months ago and there was nothing on it, I've never been convicted of a misdemeanor or felony. My definition of imprisonment would be actually taken to PRISON. It may be a dumb question, however, it's a federal government position and I don't want to provide inaccurate information. Thanks for any help.