Did you drop your steam.exe to mb2 folder and execute it? It's prob just running a different steam than the one you usually use.
Try to look for the common folder for your games it should be somewhere.
Or try to launch a steam short-cut you might always used.
Worst case might be that you just have to move your games to a certain folder if steam just decided to freshly install (for no reason).
Actuall worst case would be that you have to redownload the games which doesnt make sense though.
Like when I moved my steam.exe to my mb2 folder for a test. It installed a completly different steam client again a seperate one. It used standard settings and I had no games installed on it. Because it was using standard paths.
As soon as soon as I used my normal steam short-cut which used the normal settings it showed all the installed games.
Btw this happend to my gamedata folder after launching steam.exe once in there
(I didnt knew at that time that if the exe can't find their usuall directories it just installs itself a new client Lul)