Without the TV remote control, you cannot perform a factory reset on the TV. However, you can do a full hard reset on the TV.
To reset your TV, press and hold the power button for more than 5 seconds and the TV will automatically restart. But if the TV buttons has a lock on it, you can try by unplugging the power cord while the TV is powered on. Wait for about 20 minute until you plug the power cord back into the TV.
If these steps does not help out, you can purchase a universal TV remote control. Universal TV remote control will be available in any electronic store and they support almost all television. Read the manual that came along the universal tv remote control, install the remote and you can do a factory reset using the universal remote control