It is plugged into the

Hi and welcome to FixYa,

Sharp has made most features and functions available in the MENU. Even without a remote, the MENU button is usually on the front panel control together with the VOLUME and CHANNEL buttons on most models/versions.

Should this MENU button be available in your 27K-S300, then it would be possible to add channels in the SET UP sub menu. On the other hand, the absence of the MENU button on the front panel control would then require that a replacement remote control be purchased.

Good luck and thank you for asking FixYa.

You need the remote to get to your settings to be able to program channels. Same thing happen to mine.

Please preform Auto Channel Search in TV by going into Menu. That will store available TV channel data in TV memory and would unlock missing presets too.
If Menu is not being open by front buttons, then surely you need TV remote to do so.
Let me know exact model number and brand to find out replacement remote for your TV.
Thanks.