Unfortunately, the forums is not the correct area to ask for such a request. There is also no way to prove that you were a P-Mod in the past via this channel.
If you were a moderator previously, check out you message inbox for any messages that were sent to you and take it from there. However, if there are no messages (due to being deleted after 3 months), then really the only thing to do would be to enjoy the game as you previously did and perhaps you will be invited in the future.
As this is not really a Teamwork forum related thread, I've now closed this.