If I was to hit a truck, first I wouldn't have left and second he would have to attempt to physically assault me before I signed anything saying I was at fault.
NEVER NEVER NEVER admit fault EVER ! Facts are facts and believe it or not there are people that can pretty much figure out what happened using a few photos and a police report. Any trucking company has a few people on hand that deal only with accidents. Look at your insurance card in your car. It will say this in simple terms "NEVER ADMIT FAULT" Just let it be know if you do admit fault, well you can guess the outcome. Accidents happen in trucking every second of every day and you might still have a job if you use your head after rubbing paint.