Is this pte cc part of a chain? If yes, then write to the top of the chain, usually the mgmt and hopefully it works.
If not, there's a very real possibility that you might not get back your stuff if they choose to ignore you. You can write to them and give them a deadline to reply, or constantly call them to ask for a timeline you can expect your files. Not too sure if saying you will write to MCYS helps if you still dont't get a reply.
But so weird, why do they allow a tr who left to keep the kids' progress files? This kind of things shld be kept in sch at all time rite?