What can I do to replace an aftermarket keyless car remote?

I bought a truck about a year ago from and owner that came with an aftermarket valient Keyless 2-way remote system and I just recently lost my remote/keys. I know I can call a manufacturer to have the key replaced, but every time i use the key on the door it activates the security system and I can't start the truck. The manufacture doesn't seem to have a website so I have no idea how I can go about replacing this remote. Anyone been in a situation like this and know what i can do