Buyer gets refund and PPH states: "Buyer no longer requires work to be completed " Is this legal.

I have a buyer that was reselling my work to his client (a third party). That third party canceled the project, yet I had completed my part of the work.

So the buyer tried to cancel the job. I invoiced him anyway for $500 (which was in escrow).

At first, PPH denied the refund as the buyer was canceling for no fault of mine.

Next the buyer offered $50, and I refused the invoice asking for a refund.

Now PPH has refunded $450 of the escrow with this reason:

" Buyer no longer requires work to be completed "

I can't find anywhere in the terms that a buyer can cancel the project when work is done.