This is Implementation specific and depends on how eNB detected this dtx. If UE sends NACK and DTX is detected then Retx will be helpful. If UE itself missed the PDCCH or sends ACK then Retx is of No use, because UE will move to Inactive once Inactive timer expired. Ue will run Retx timer only if it sends NACK . Depends on this scenario eNB has to decide on Rex.