Who owns the RAW video, audio and photo footage in case the client does not pay the agreed price?
Copyright law here says that the person who shoots the footage owns the footage. The only way to change this is if you sign a work for hire contract which says that the production company owns the copyright and that they'll pay you in exchange for your work and copyright. If they didn't pay you then they breached their contract. If there was no contract then you own the footage and don't have to give them anything. Something as simple as an email could be considered a legally binding contract though. I suggest you contact a lawyer who knows entertainment law in the US.

Save everything, emails, phone call records, written notes, receipts, plane tickets, reservations, anything that demonstrates your working relationship with this company and how much they have paid you and how much they owe you or should have paid you.

Sorry this sort of thing happens. 

See here:
http://en.wikipedia.org/wiki/Work_for_hire