Goalie,
Good question. If I understand you correctly, you killed a full hog when under danger at a base and got killed in the process, re-spawned at the same base and are now wondering whether or not you are required to take the hog that you had killed before you died. I know Booyah usually answers these questions and I'm sure he will give his thoughts on it a little later. If I have understood your situation correctly, when you respawn you are not required to get in the specific hog you had killed prior to dying, simply get in the chain or rocket hog closest to you and get out of the base or possibly load up with a teammate. You are NOT required to take the hog you had killed prior to dying. If that was required then people would be walking to hogs instead of getting into a hog closer and racing to there next nav which would cause more problems.
Hope I cleared it up, If you have any questions about my explanation feel free to PM me. As I said, I'm sure booyah will post his thoughts on this situation in a little while.
Thanks,
ReF