Verify whether Apache serves cached pages

I've discovered today my site was not serving cached pages - though it did before. The thing is that I did not check the Boost signature in the anonymous pages for a long time, and I was upgrading Boost as the versions increased.

So I've looked into it, tried all kinds of server variable combinations, .htaccess changes, different settings, etc. I tried also the dev version of today. As admin I could see Boost is generating cache, but the signature was still missing on anonymous pages.
One difference I found on this site vs another one where Boost still worked (both are multisites) was that the generated output storage was 'normal' for both that and for gzipped pages, while on the other site I had the first one empty and the other 'gz'. I also emptied the 'cache' folder completely.

I was changing things, wasting time, until I went completely confused and I went to the most drastic thing -- disabled Boost, uninstalled it, then installed 6.14.

Installed the generated .htaccess code and things worked out of the box.

Now, I say all this to make a case for a tool that would actually check whether Apache does serve cached pages.
Back here you told me "The boost block only checks if the pages cache got generated. It would be hard to make it check to see if apache is serving it as well."

But above you can see how difficult and frustrating it can be to not know when Apache stops serving cache, perhaps after I upgraded to particular version of Boost, or perhaps changing some settings.

I propose you build in a little function in cron that would fetch a published page on the site that is not disallowed in Boost settings etc (or perhaps a user can specifically set which page can be checked), fetch it anonymously, look for signature, if not there, fetch it second time, and if still missing, set an error message in watchdog.

What do you think?