Are you saying you sent XCP to your BTer funding XCP address, but forgot to attach XCP?
Then you didn’t send anything.
If you mistakenly sent something else to your BTer address for BTC (I don’t know what, but let’s say you sent BTC), you’d have to ask them to return it to you. As with all bitcoin sends, once you send something it’s gone (unless the guy who received wants to return it to you.)
(Also you’re the only person in control of your wallet - noone can override any transaction that happens on the bitcoin blockchain which is used by Counterparty (and bitcoin, of course).)
If you sent XCP to your BTer funding address for BTC, then that’s another situation where you’d need to ask them if they can recover your XCP from that account.