I've tried looking through my entire computer for it, including the bin folder it should be in, but it's not there. I've also tried deleting my bin, verifying game cache integrity, then redownloading the bin, to no success. I also borrowed montanium's exe, which claimed steam wasn't open, even though it was. Any ideas?

Sure its not here?

Its hidden in there quite cleverly.

try to close steam
restart your computer
start steam
try to launch a game, see if you can launch the game without a message saying you can't connect to the steam cloud.
if this all works try to locate the p2map_publish in steamapps/common/portal 2/bin
If it is not there, DELETE your portal 2/bin folder
try to validate the game cache