Is this the MVD2016BLK model? I'd like to post these results at hifi-remote.com, but Memorex from target is not enough description to make it useful.

Fav buttons date from when people wanted to store a few channel numbers in the remote, and cycle through them. Too many channels are available now to make that a popular approach.
Anyway, the Fav button on older remotes is frequently a kind of multi-macro key. Each push or repeat of the button sends upto 5 IR signals to the component (usually a TV). So UEI set it up so that key can't be assigned an EFC.