How come Apple, Cisco, Oracle, etc. didn't find Heartbleed?

As I understand it, Google did find Heartbleed:The flaw was first reported to the team behind OpenSSL by Google security researcher Neel Mehta, and independently found by security firm Codenomicon. Read more: Here’s How To Protect Yourself From The Massive Security Flaw That’s Taken Over The InternetRead other answers by Travis Addair on Quora:Do Google