If your garage door opener has a Yellow Learn Button, it utilizes Security+ 2.0 technology (source).
In these units the simple wall button is replaced with the control panel communicating via the proprietary (and agressively defended) serial protocol. Affected units include AssureLink models from LiftMaster, Chamberlain and Sears.
Some of the compatible remotes are 882LM, 883LM 891LM which at the time of writing can be purchased for under USD 20.
Please post your questions and install reports with your Security+ 2.0 units.