If you actually deleted them then the only hope of getting them back is to contact admin or a moderator and ask for pity.
I have a similar problem. I relied on the software to correctly save my PM's before I deleted them. Only later did I find out that the software didn't work correctly, so the recipient on the sent pm's was not saved. Oh well... Because of that glitch in the software I think there just might be a chance that we might be allowed to recover some of the lost data, but it will be up to the admin to make it happen.