Hi there,
Sorry, I did not get on that much over the weekend.
The support
SHOULD have made it clear to you that the existing (new) characters would be deleted when the merge occurred (gPotato IDs are incompatible with new my.com characters, the account has to be cleared for the merge to work..), and given you the option of letting the account be rest (and the characters be deleted), or providing them with a second my.com account to merge the old characters onto.
You can ask in the support ticket if its possible to recover those deleted characters and put them on a separate account (that you should register) how ever I do think those characters are gone for good.
There are adjustments being made to the support system template to make it clear that the merge process will require a wipe of the my.com account if any existing data is on it (having logged in, or having created any characters to use in the mean time, but unfortunately they are not ready yet..
-Wraith
Edit:
please PM me with the ticket ID so it can be checked.