lots of issues with damage caused by construction sites i.e. "The big digg" I'm sure you've heard about it. Thry getting anything out of the City/GOV but be late on your taxes and they'll screw you. It's the fact that you don't have any witnesses, if you had called the Police at the time it happened.. then yes you have more leverage. But now you have to proove that it happened there and their equipment caused the damage. Regarding GOV sites remember they don't like to pay anything and that goes with potholes, I had a friend that his BMW's front suspension was damaged by a utility cover that was off, he riped the spindle right off all he could do is put it throught his insurance CO. I feel your pain man, I've been there but as ridicuous as it may sound you need solid proof and from hearing your story it doesn't sound like you have much exept dry concrete. Seriously good luck man, contact your insurance Co. that's what they are there for and have them fight for you but also contact a lawyer, if he/she doesn't charge you for advice.
Still letting it all sink in... and loving every minute of it!!