Codenomicon, the company who actually named the flaw, didn't find the bug via the source code. They were building a security product and when testing that product against their own servers exposed the flaw. Open Source was not a factor in this discovery.
Google HAD discovered the flaw via the source code, exactly two days earlier.
In this case, the bug was 0.267379679% more discoverable due to being open source versus being closed.
Devil's Advocate...
Codenomicon, the company who actually named the flaw, didn't find the bug via the source code. They were building a security product and when testing that product against their own servers exposed the flaw. Open Source was not a factor in this discovery.
Google HAD discovered the flaw via the source code, exactly two days earlier.
In this case, the bug was 0.267379679% more discoverable due to being open source versus being closed.