Just because it happens all the time, doesn't make it right...

If the 3rd party processor is keeping the money, never returning it to the reseller, they are wrong. After x amount of time a cheque should be cut and sent, account closed, just like banks do with inactive accounts. It isn't their money, and they send out a notice, because people forget. It's the law, least up here, and if they don't respond, then it goes into some reserve of some kind, that they don't get access to, but I think defaults to the Government.

No response, then perhaps to the sponsor, but the 3rd party should after x amount of time, contact and then close the account.

my two cents