Webcam not found on Thinkpad E550 (ubuntu 14.04)

There is a bug for your webcam, it seems that it's not supported yet:
Acer, Inc ID 5986:055a is useless after 14.04.2 installed

Please subscribe to that bug to get you updated.
Also, you can click on the This bug affects # people. Does this bug affect you? string to state that you're affected by this as well.

Or you can patch it by yourself with a patch (ignore_chining_errors.patch) provided in:
http://sourceforge.net/p/linux-uvc/mailman/message/34182460/

By following instructions here to build your own kernel.