Oh no, not again! Teories abound. The official statement [here]by the party hints at the possibility that the two have been taken, against their will, by rival party Umno. RPK goes one up, confirming here that the two are, indeed, in Umno's hands.
I am reminded of the PKR Member of Parliament who went missing last August. Remember the story? Refresh your memory here. Lots of accusations were made against the Police and Umno/BN when he went M.I.A. after the conversion forum.