Having worked in auto claims for a major insurance company, I'd suggest reporting it. If you had merged into the lane and were stopped (as your posts suggest) then the truck driver is definitely at fault. However if you were both moving at a merge area, it's harder to figure. Was the merge one where your lane disappeared, or were both lanes being channeled into one?
As far as the insurance information, in the US you do have to give your insurance information in an accident, if asked. The cop should have at least made sure that info was exchanged. Hopefully you got the license tag # of the truck, and it isn't an expired tag. Did you get the name of the company, usually written on the side of the truck?
On the police report, you can get the officer to amend what he wrote. If you talk to him so he remembers the situation, he may be willing to do that for you.
Overall, merging accidents suck. Liability is often not clear, and both people think the other is at fault. If you have collision coverage, your insurance will likely end up paying for the damage, minus your deductible. If not, you'll probably end up paying for your own damages.
PM me if you'd like some more discussion on it.