Your very false assumption is that Google engineers would have access to the code in the first place.
So you claim they wouldn't have access to their own Android code (you know, where the bug lies).
Droid is a Motorola phone on the Verizon network. Google is one of many participants in the Open Source Android project, which Motorola wisely chose to use in this case. In the past they have used Linux, but they have never went Open Source in the application domain. This meant that in the past, an Autofocus problem would need to be fixed by Motorola engineers. Since it was closed source only a few Motorola engineers would have access to, and famliarity with , the code.
If the code in question was really a bug in Motorola's code then it would have most likely been proprietary software and as such as you claim Google wouldn't have gotten access to it. That Android itself is released open source under the Apache 2.0 license doesn't mean that the customized versions created by say Motorola is going to be open source. So actually, your the one making false assumptions that go against the very words of Google's own people.
In case you are still not getting it, try looking at your broken "Google would work on it anyway" argument this way:
Why wouldn't they work on their own code base?
Number of Open Source handset projects in which Google is Involved: 1 or more
You do realize that most of the changes Motorola did to customize their version of Android are proprietary right? And that the phone manufacturers are under no obligation to open source their additions. But this is all moot since the bug is an issue in the base Android itself.